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slipknot66
09-01-2007, 09:13 PM
Im having problems to download both files (Emil3d, myself44)
Corrupetd files.

Emil3d
09-01-2007, 11:16 PM
Hi everyone, recently I finished reading the entire thread VRay-like interior renders with mental ray??? (http://forums.cgsociety.org/showthread.php?t=190232) and decided to test my MR skills with what appeared to be the most popular testing scene in that forum, the famous classroom. There are great examples of superb MR skills like the scenes from Dagon and many other very skilful MR users. I would like to say thank you to all contributors for sharing their skills and renderings.

Although some of those great scene examples were posted at different times, most links are currently dead and some users like me are not among the lucky ones who were able to download those treasures. I found that examining scenes that demonstrates the best of MR from skilful users is much more useful than reading the entire MR related help a million times. Unfortunately there are no scene examples that can serve such purpose included in the official Maya documentation.


I found the classroom scene after a Google search only in Max format. Although it opens fine in Maya and comes with a few non essential geometry problems, all objects have bad or missing UVs so I had to spend about a long day fixing these to some acceptable degree.

I decided to create this thread after participating in another thread in this forum Physical Sky and .... moon ? (http://forums.cgsociety.org/showthread.php?f=87&t=530419&page=1&pp=15) where I used my tests to share my tone mapping and color correction experiences. MrHoo asked me if I would share the scene and I decided to use the opportunity to create this thread as a place where everybody should be able to download the test scene at any time with lighting, materials, and settings set from different users to their best capabilities who are willing to share back the scene after improving it, sharing different possibilities and techniques, or simply contributing to it in any way.

Additional different testing scenes are welcome in this thread. This should be a place where users can also ask and receive help with solving problems associated with shared test scenes. I would like this thread to be limited only to solving problems and sharing skills associated to or demonstrated with shared scenes. So that users can download, open, examine, and test render the scenes themselves instead of only seeing great renders with a few posted settings that remain mystery for many users.


The most important thing it to keep all links and uploads alive at all the time. Any tips on how to achieve this successfully are very welcome. On my part I donít mind downloading posted scenes and upload them on my space on http://rapidshare.com/ (http://rapidshare.com/) in case an original link dies.

I hope this thread turns really helpful

Emil3d
09-01-2007, 11:17 PM
This is the classroom scene file just converted from Max to Maya 8.5 without any further changes. class_final_vray_reset.rar (http://rapidshare.com/files/52689508/class_final_vray_reset.rar)

This is the same scene file but after I modified it. class_room_shared.rar (http://rapidshare.com/files/52689281/class_room_shared.rar)
If you have trouble with the .rar file this is a .zip version of it class_room_shared.zip (http://rapidshare.com/files/52766154/class_room_shared.zip)
The most important changes are:
The scene was scaled to more realistic dimensions. UVs were applied to all objects. There are no textures in the scene yet. Some geometry was cleaned up. Materials were assigned to the objects. The scene was organized in groups and layers with English description of objects and materials (if my English has failed you are free to correct it). The scene was lit only with physical sun and sky environment. If you render the file using Render View the result should be similar or better to this.

http://i111.photobucket.com/albums/n129/Emil3d/RenderViewResult.jpg

I said similar or better because this image is blurred. And it is blurred because it was first batch rendered to openEXR float x 32 bit file with the mia_exposure_simple disabled and then tone mapped with it using the preview options and color corrected with the addition of HSV remap and Contrast utility nodes. This process is illustrated in more details in the second half of post #12 from this thread (http://forums.cgsociety.org/showthread.php?f=87&t=530419&page=1&pp=15).
And this introduces the first of many problems that I have with these test renderings:

Problem 1
Blurred result when using the preview feature of mia_exposure_simple comparing to the sharpness of the rendered file.
To reproduce this, first batch render using the modified scene after disconnecting Contrast utility from the Lens Shader slot of the camera. Next, connect back the Contrast to the Lens Shader and in the mia_exposure_simple node, check the preview box, and for a preview choose the rendered file. The blurring effect will become more obvious if the image used for the preview was rendered with Gauss filter set in the Anti-Aliasing Quality section of the Render Settings. Provided there was no problem with the blur this process could be very useful as node based post color correction solution for any HDR image.

Problem 2
This is not really a troubleshooting problem but rather sharing issues Iím facing that might be common among other users too.
How to achieve a desired goal when tone mapping and color correcting HDR images with the available options, tools, and different programs?
As most of us already know the linear High Dynamic Range images do not fit properly in the limited range and non linear gamma of our monitors. This requires a tone mapping and color correction that is mostly based on userís eye and perception.

The following examples show my experiences with this:

Method 1: The image shown earlier in this post is what Iím capable to do so far directly in Maya. There should be no blur if the image is rendered using mia_exposure_simple at render time instead of used as a preview. I already described how to reproduce this result in Problem 1

Method 2: the image below was edited in Photoshop by using Exposure, Curves, and Selective color commands.

http://i111.photobucket.com/albums/n129/Emil3d/PhotoshopCCResult.jpg

You can reproduce this image if you batch render using the modified scene after disconnecting Contrast utility from the Lens Shader slot of the camera and then in Photoshop run this action (http://rapidshare.com/files/52689061/CC_for_classroom_shared.zip) on the rendered image. This took me a lot of tweaking of the Curves and I never got fully satisfied from the results neither as tonal range nor as colors. Like with all other methods the challenge is to reveal details in the bright and dark areas without flattening the image too much and keeping some pleasant contrast but I wasnít able to make it both ways. May be the fact that the scene is with somehow boring colors, lack of textures, and just one light source coming from the environment, makes this more challenging but I feel the image can be improved much more than what Iíve done so far.

Method 3: the image below was also edited in Photoshop with a process illustrated in more details in the first half of post # 12 from this thread (http://forums.cgsociety.org/showthread.php?f=87&t=530419&page=1&pp=15).

http://i111.photobucket.com/albums/n129/Emil3d/PhotoshopCCR_LayersResult.jpg

I rendered this image form an earlier slightly different stage of the scene. The most noticeable differences are the darker color of the blackboard and less FG artifacts on the walls at the upper right corner of the scene because it was rendered with slightly higher FG Accuracy of 150 and Point density of 1.2
This method requires most involvement but gives more control, although my result is far from perfect.

Method 4: this image was edited with Artizan with the following settings.

http://i111.photobucket.com/albums/n129/Emil3d/Artizen.jpg

http://i111.photobucket.com/albums/n129/Emil3d/ArtizenSettings.jpg

This took just a few seconds which is a pretty good result for that time and the good thing is that, like with tone mapping in Maya, the image stays always at 32 bit. Iím using Artizan just by intuition without ever bothering reading or learning how to use it and it is very easy and fun to use. However Iím still new to it and havenít found more localized control like curves. As you can see on the image the nicer contrast comes at the expense of pale and almost colorless environment color seen through the windows and the direct lit areas of the walls. This is easier to fix in Photoshop with the use of more localized controls.

As you can see all these different methods have pros and cons with different possibilities and this is not necessarily bad but with each method I feel limited to the capabilities of the deferent tools. Of course my skill level may be also a factor in all this and I will really appreciate if other users share their workflows.

Problem 3
is the biggest mystery I ever had. If you compare all images here looking under the window sills and the heater you will notice a strange illumination difference between some of the images. The image displayed in the Problem 2 > Method 3 above and all of the partial images displayed in the last Problem 4 paragraph donít have that strange illumination under the window sills which was not there in an earlier stage of the same scene. Initially I thought that this is caused by some differences introduced between the 2 stages like the scaling, UV mapping, cleaning of some geometry, and realignment, but after some crazy tests without finding what causes this, I decided to render again directly from the file that rendered the no problem images. To my total dismay the same file that previously rendered images without this problem now renders a different image showing this illumination problem. Iím 100% sure the file was not changed between the 2 renderings. Every time I batch render I save the file and continue with a new version of it. Not only that but Maya automatically produces a temp copy of the scene ending with some 4 digit number and the copy stays until manually deleted. On top of this I have more stages saved as different files before and after and all of them now render with this problem. There is no way I could have accidentally change so many copies in the same way. The only thing that was not the same between the previous and the new renderings was the rendering resolution which I believe should not affect things like that.

Here the 2 images were rendered from the same file Ė the larger is rendered earlier with 1000 x 750 and the smaller image was rendered now with a resolution of 320 x 240 from the same file. The screen shot was taken from imf_display with the same gamma applied to both just to make them brighter for better viewing.

http://i111.photobucket.com/albums/n129/Emil3d/Ghost_Difference.jpg

You can clearly see the difference with the illumination problem. What the heck is going on? Is my copy of Mental Ray possessed by a ghost? Please let me know if this problem shows on your ghost free computer when you render the shared scene from the link. At one moment I thought this could be Mental Ray reading some old Final Gather maps since I have a folder full of them but I triple checked before the troubleshooting test renderings that the Rebuilt is set to on and even deleted names of any Final Gather maps from the Render Settings. I even made a test with removing all objects from the scene except the walls and the problem only became more obvious. If you render this scene with the problem still showing and find whatís causing it you will remove the biggest mystery Iíve ever encountered in Maya.

Problem 4
Iím experiencing big performance hit when rendering glossy mia_materials with high Reflection Gloss Samples. Notice the noise on the top and shelf of the desk, floor, chairs and the blackboard stand. In the scene, those most glossy materials are currently in a separate bin and set to 256 Reflection Gloss Samples. This noise become more obvious and unacceptable with lower samples and will only go away with much higher samples. The problem is that the rendering times increase exponentially when this value is raised.
Here are some noise examples of different Reflection Gloss Samples:

32 Reflection Gloss Samples

http://i111.photobucket.com/albums/n129/Emil3d/ReflectionGlossSamples32.jpg


64 Reflection Gloss Samples

http://i111.photobucket.com/albums/n129/Emil3d/ReflectionGlossSamples64.jpg


Even with 256 Reflection Gloss Samples the noise although greatly reduced is still there and renders about 7 times slower than 32 samples. On my slow computer this takes a lot of hours.

http://i111.photobucket.com/albums/n129/Emil3d/ReflectionGlossSamples256.jpg

Any tips how to speed up rendering of glossy materials with preserving acceptable quality will be greatly appreciated

I certainly can list more problems associated with this scene but I think thatís enough for now.

Thanks for reading all this. I appreciate your feedback and contribution.

Emil3d
09-01-2007, 11:34 PM
I would like to see this thread growing to become a render scene archive. It would be cool!
Emil3d, Im just asking now how do you tonemap a EXR file in Photoshop ? This format seems so limited in PS, no new layer creation, no image adjustment... what is the method of tonemapping a 32 bit EXR in Photoshop?

Also, is it normal when I open your classroom scene, all objects are green, all materials are "unknown", and when I render, everything's grey ?...
http://i14.photobucket.com/albums/a350/myself-44/class.png

Ömyself44 thanks for contributing:thumbsup:.

Yes, Photoshop has very limited options for 32 bits per channel images but I convert them to 16 bits after applying the exposure command. You can reproduce and see all my Photoshop actions by following the instructions from Problem 2 > Method 2 section from my previous message. You have to download, extract, and use the action file in Photoshop from the provided .zip file from the link. In case you are not familiar with how to use the action file here is a quick guide:
Open the rendered x32 bit image in Photoshop SC2 or newer (you can try this with any file but just to see actions). Choose Windows > Actions (or press F9) to open the Actions palette. From its pop up menu, choose Load Actions and choose the action file which name is CC for classroom_shared.atn. It will appear as a folder in the palette. Expand the folder, Action 1, and double click on each action in order to open its dialog window so that you can examine it and apply it.

Regarding the problem with properly rendering the scene, I donít know whatís wrong but make sure that you open properly the file by first coping it to the scene directory of your current project and then use the Open command from Maya.
Also I can see from you screenshot that you are using Maya 8.5 without service pack 1 and this may be causing the problem. You can upgrade to service pack 1 here http://www.alias.com/glb/eng/support/maya/updates/pages/maya_85_release_notes.jsp

Emil3d
09-01-2007, 11:36 PM
Im having problems to download both files (Emil3d, myself44)
Corrupetd files.slipknot66, thanks for you interest, your participation in this forum is very valuable:thumbsup:.

I test downloaded the files from the links in my message as well as the file provided from myself44 and both opened fine. Iím not sure why you got them corrupted but it might be because we are using .rar files. I provided a new link at the beginning of my previous message with .zip file which is larger size but may be more robust against internet travel corruption:). I hope it works for you.

myself44
09-02-2007, 01:56 AM
I would like to see this thread growing to become a render scene archive. It would be cool!
Emil3d, Im just asking now how do you tonemap a EXR file in Photoshop ? This format seems so limited in PS, no new layer creation, no image adjustment... what is the method of tonemapping a 32 bit EXR in Photoshop?

Also, is it normal when I open your classroom scene, all objects are green, all materials are "unknown", and when I render, everything's grey ?...
http://i14.photobucket.com/albums/a350/myself-44/class.png

---

Then, I'll contribute a bit by uploading one of my old interior test I did. I modified it to apply me newly learned methods. Before I would like to precise that scenes and any files posted here are for practice and personal use only.
I archived the scene file and all the textures that come along. Scene elements name are in English. I've left pretty much all settings to default so that ppl could be free to adjust to their wishes.
*Download links at the bottom of the post. (I also uploaded to Emil3d's RapidShare account.)
When scene is opened and rendered, it should look like the image that follows (quality could be improved afterwards; I wanted a fast render to show to overall lighting)

Overall description :

- IBL enabled (sky color)
- Physical Sun&Sky disabled, no mia_exposure
- 1 Maya Area with MR Area enabled. 50 000 photons; rest default
- 1 Maya Area with MR Area enabled. 30 000 photons; rest default
- 1 Direct.light sunlight. Rest default
- Render settings. Low GI and FG values.

http://i14.photobucket.com/albums/a350/myself-44/3D%20projects/interiors/squareRoom.jpg

Quick adjustments made in Photoshop with Levels, Brightness/Contrast, Shadow/Highlights.
And let's hope, a lot of ppl will post up their scenes to the profit of everyone.

http://i14.photobucket.com/albums/a350/myself-44/3D%20projects/interiors/squareRoomPost.jpg


---> FileFront link (http://files.filefront.com/ZhiyaoRoomrar/;8456611;/fileinfo.html)

MrHoo
09-04-2007, 08:10 AM
Hi Emil3D

sorry, I saw this thread only now and i am currently at work and can not read it concentrated.
So I will do that at home and will participate strongly in testing and sharing results :-)

I am glad about this thread because it gives me a great opportunity to step in a very early stage of the topic and grow with it

Thanks!

Cu

Dominik

modernPrimitive
09-04-2007, 05:34 PM
OKay,

I'm totally confused. I downloaded the classroom scene and did a quick test render - I noticed that there was no GI but only FG enabled?

Last time I checked (Maya 7.0) this kind of lighting was impossible with FG only. One had to use GI and then smooth out the results with FG. Is GI becoming redundant?

The other thing was that accoding to the theory FG was a "fake" rather than a true light model - something like compositing the result of an occlusion pass with a beauty pass - has this changed? The results in the classroom render above one can only get from more than one diffuse bounce but FG unlike GI is supposed to only bounce once?

Whats happening?

myself44
09-04-2007, 09:52 PM
OKay,

I'm totally confused. I downloaded the classroom scene and did a quick test render - I noticed that there was no GI but only FG enabled?

Last time I checked (Maya 7.0) this kind of lighting was impossible with FG only. One had to use GI and then smooth out the results with FG. Is GI becoming redundant?

The other thing was that accoding to the theory FG was a "fake" rather than a true light model - something like compositing the result of an occlusion pass with a beauty pass - has this changed? The results in the classroom render above one can only get from more than one diffuse bounce but FG unlike GI is supposed to only bounce once?

Whats happening?

In Maya 8.5, a Physical Environment can be created and this will add a sunlight. As for the 'FG only', it's by using multibounce feature. Someone could give more detail and info on this aspect because Im not very familiar either.
But personally, I still prefer to use area photon light in combinasion with FG.

MrHoo
09-06-2007, 04:08 PM
Hey folks

i did this render yesterday with the render settings of Emil3D's classroom scene.

I am quite happy with the result (render time 19 min. on my particular system) but there are to issues wich I recognized:

In the red circle on the bottom of the table I think it looks quite unnatural, because there are no shadows of the table legs.

Also the floor shader has a bit reflectivity (like the floor in Emil3Ds classroom scene) but you can not see any reflections.

If you have suggestions share it with me :)

All materials mia_material

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior.jpg

thanks

Cu

Dominik

hkspowers
09-06-2007, 06:34 PM
Just render an ambient occlussion pass and your legs should look fine. Great image!!

floze
09-06-2007, 07:25 PM
Hey folks

i did this render yesterday with the render settings of Emil3D's classroom scene.

I am quite happy with the result (render time 19 min. on my particular system) but there are to issues wich I recognized:

In the red circle on the bottom of the table I think it looks quite unnatural, because there are no shadows of the table legs.

Also the floor shader has a bit reflectivity (like the floor in Emil3Ds classroom scene) but you can not see any reflections.

If you have suggestions share it with me :)

All materials mia_material

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior.jpg

thanks

Cu

Dominik
Are you sure all objects have 'Visible in Reflections/Refractions' flags set to ON? When importing objects, with some maya versions and certain import formats (.obj) these flags are set to OFF by default.

royterr
09-06-2007, 09:26 PM
you need to increase the number of rays in 4 places:
- light shadow rays (light options)
- shadow rays (render globals)
- raytrace reflec/refrac rays (render globals)
- FG reflec/refrac rays (render globals)


add an ao pass for more shadow details.

modernPrimitive
09-06-2007, 10:11 PM
Hey folks

i did this render yesterday with the render settings of Emil3D's classroom scene.

I am quite happy with the result (render time 19 min. on my particular system) but there are to issues wich I recognized:

In the red circle on the bottom of the table I think it looks quite unnatural, because there are no shadows of the table legs.

Also the floor shader has a bit reflectivity (like the floor in Emil3Ds classroom scene) but you can not see any reflections.

If you have suggestions share it with me :)

All materials mia_material

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior.jpg

thanks

Cu

Dominik

Awesome render. Just some constructive comments:

1) The couch looks a bit CG-ish in places - almost like the FG is too spread. An AO pass would also add some shadow detail between some of the cushions where it's too soft. Some parts look perfect - like the right hand cusions but the shadows under the "sitting" cushions need more shadow detail.

2) The corner where the walls meet looks unnecessarily occluded. This is quite standard result though with FG and GI - I think it's something to do with the falloff or spread of the FG occlusion but I'm not sure how to fix it as I haven't played with GI and FG since 6.5.

Can anyone suggest how one would get less of a spread / softness with regards to the occlusion because I think this is where FG starts to look a bit unrealistic. I realise this softening and spread is to help reduce flicker but how does one change the spread - radii perhaps?
Try a test render using amb_occlusion (no FG) and then the same scene with FG_occlusion (with default FG settings) and you'll see what I mean. What needs to be tweaked to find the happy medium between render time and better occlusion?

MrHoo
09-07-2007, 07:46 AM
Hey guys,
thx for your replies.
@hkspowers
Yes, i thought about it before, but I would like to have it in the normal render also :-).
I also used already the built in ambient-occlusion in the mia material

@floze
'Visible in Reflections/Refractions' is on, because I modeled all models from scratch and didn't import any objects.

@royterr
I cannot increase light rays, because I only use Mr sun/sky, and in the direct light options there are no shadows enabled (if I am not doing wrong now)

Raytrace reflec/refrac rays and FG reflec/refrac rays have already been increased.

I think I only forgot the shadow rays, but I am not sure now, I have to check it later at home...

@modernPrimitive

Yeah, you are right. I think the problem is that I used mia built in ambient occlusion with the sofa and the walls. I'll try to switch it off and render seperate mib_ambient_occlusion layer.

It was quite hard to lay out the uv's of the sofa, because I am such a noob in uv's and I think I did it not perfectly or not in the right way... but I will fix it :-)

So I will try to improve the whole scene, remodel some objects to get it more realistic (like the strange lights :-)) and add more objects...

see you soon - very good thread (Emil3D)

Thx

Dominik

modernPrimitive
09-07-2007, 12:06 PM
hmmm.....and now for some animation...

We've just done an interior animation with an animated sunrise to sunset. Still getting some artifacting, which we're partly cleaning up in post but it's approaching acceptibility.

Res: 1000x500
Rendertime: 4min per frame on an AMD X2 3800

Will link to a clip sometime when we've tweaked a bit more.....

MrHoo
09-07-2007, 01:26 PM
Hey,

I did the image below now with occlusion pass...
A lot better I think, but I get the shadows under the table back (caused by the glass surface, which I wanted to get rid of it by increasing the fg rays in refraction).

I could probably avoid that by not affecting the glass surface by occlusion shader - I will give it a try these days...

There's still a lot to do - increasing the fg point size to get rid of the speckles, for example...

I could unfortunately not use the ctrl_occlusion shader, because it is not compiled for a 64bit system. That's a pitty!!!

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior2.jpg

Ok, thx for viewing and posting comments and critics

Cu

Dominik

MrHoo
09-09-2007, 04:43 PM
Hi folks,

some update with sky multiplier 1.15 and some reflections...

I am not perfectly satisfied but it is going in to the reight direction

Cu

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior3.jpg

myself44
09-09-2007, 06:09 PM
MrHoo
Nice scene, I've been following this since a while
What really catch my eye is your sofa model... it looks so real !
So I was wondering if you can tell me your method of making the bump map for the cushions...and also did you used a mia_material ?

keep updating, looking very good

MrHoo
09-10-2007, 06:30 AM
Hi myself44,

I used a fabric texture (I think from cgtextures.com) for the bump, which I repeated several times and yes, I used mia_material. Actually all materials in the scene are mia_materials...

I am not satisfied with the floor. I want to achive realistic ceramic-tile look, but it works not perfectly. I have got a map in the refl_color slot and another for bump, but I get this speckle reflections. I have to tweak a lot more I think...
Time consuming...
So if anybody has got ideas for cool realistic stone (ceramic) tiles, like bump mapping and refliction mapping workflow, share it with me please :-)

So, I'll will add more items like pillows, shelves and so to the scene soon.

Stay tuned

Dominik

Emil3d
09-11-2007, 04:32 AM
Hey, Iím glad to see this thread going nicely.

@ MrHoo, beautiful test renderings:thumbsup:. Mapping of the reflections and bump of the ceramic floor is a good decision. For the mia_material, the reflections can be controlled from the BRDF view sliders [have in mind that they misspelled the order of the names Ė the correct interpretation should be: first slider = facing to view, and the second slider = perpendicular to view]. If both sliders are at their maximum you will have reflections at any angle. Have in mind that these values have no effect if Fresnel option is on, then the angle of reflection is controlled by the Refraction Index value. Also from the BRDF Curve and Reflection Color you can control the strength of the reflections. Your first image didnít have reflection on the floor but you manage to pull some on the second image, did you find out how to control this?

Also it would be nice if we share scene files. Then this thread will truly deserve its name. Sharing test scenes will allow us to share and improve our knowledge more effectively. When examining a scene, one can directly fix problems, improve, learn, contribute, and share back the scene.
Of course if your scene has elements with commercial values like models, textures, etc, or you are not allowed or donít whish to share the scene, you can as you already did, just post renderings. Although if you whish you can partially share a scene or a quick proxy model of it. For example if you canít share the sofa, the table, and the textures in your scene you can delete them and post the scene with some rough blocked out geometry as a substitution. A test scene like that would be enough to trace a problem like the lack of reflections on the floor.

Anyway tanks for sharing your progress and the great renderings. Keep up the good work:thumbsup:.

Emil3d
09-11-2007, 04:41 AM
OKay,

I'm totally confused. I downloaded the classroom scene and did a quick test render - I noticed that there was no GI but only FG enabled?

Last time I checked (Maya 7.0) this kind of lighting was impossible with FG only. One had to use GI and then smooth out the results with FG. Is GI becoming redundant?

The other thing was that accoding to the theory FG was a "fake" rather than a true light model - something like compositing the result of an occlusion pass with a beauty pass - has this changed? The results in the classroom render above one can only get from more than one diffuse bounce but FG unlike GI is supposed to only bounce once?

Whats happening?I think originally GI and FG was designed as different lighting techniques. In practice however GI on its own never succeeded as much as FG and people use GI + FG or only FG, so practically one can consider GI + FG and FG as different lighting techniques. While GI stayed unchanged, FG was improved by adding multi bounces and increasing its performance. The principal differences between the two techniques however have not been changed. It helps to have a certain degree of technical understanding about how Mental Ray uses these lighting techniques to add light contribution to the shading of each pixel on the image. Then one can decide how true or fake each technique is. For me they are both much more fake than true but GI ray bouncing technique is truer as a simulation model. The ray bouncing starts from the light and goes to the point being shaded which is how the light travels in real life. In my experience however the result from using only GI is anything but convincing.
With FG a bunch of rays shot in a hemisphere above the point being shaded travel to the first hit nearby objects to calculate the average color, so the light contribution is rather indirect. Multi bounces will simply repeat this which will become very inefficient with more than a couple of bounces. On practice however FG on it own give more acceptable results than GI because of its smooth and consistent shading.
Using both GI and FG is probally the best for certain situations.

MrHoo
09-11-2007, 06:47 AM
Hey Emil3D,

thx for your comments. I am going to share the scene as a test scene, but I will first clean up a little bit and try to arrange it, so that everybody can open it. Give me one or two days.

Also I solved the reflection problem yesterday, and I think I am quite happy with the result, but i can post pictures at least tomorrow...

I made a layered texture with contrast node to control bump. Works quite nice :-)
In the refl_color there is a simple picture to control reflectivity of the tiles.

You can have a look on it when I post the scene.

So keep it up

Cu

Dominik

MrHoo
09-11-2007, 04:38 PM
Hey guys

I uploaded my scene as test scene at rapidshare:

LINK (http://rapidshare.com/files/54964010/hoo_interior.rar)

Please understand that I removed the models (sofa and lamp) and replaced it with simple cubes.
You can freely add objects for your test renderings. Please do not use the scene for commercial projects ( I think you would not because its so! simple) :-)
If you post it anywhere else then here, please link my name to it.

Thanks and have fun

(I hope it works :-))

Greetz

djltrain
09-11-2007, 08:14 PM
i have been playing around with 8.5 for sometime now and still feel like a complete noop on the sun/sky thingy. How do you control the photons comming off of the sunlight? i get this all the time and have to add area lights to throw photons around the room but i like the look of just the sunlight. i have opend and used all the same settings as you guys and it just wont work

here is my stuff to look at if you could help that would be great!

MrHoo
09-11-2007, 08:45 PM
...and an update...

http://www.art-or-silence.de/ext_bilder/cgtalk/test_interior4.jpg

I think the bump or reflection is a little bit too strong

what do you think?

Cheers

Dominik

MrHoo
09-11-2007, 08:48 PM
i have been playing around with 8.5 for sometime now and still feel like a complete noop on the sun/sky thingy. How do you control the photons comming off of the sunlight? i get this all the time and have to add area lights to throw photons around the room but i like the look of just the sunlight. i have opend and used all the same settings as you guys and it just wont work

here is my stuff to look at if you could help that would be great!

Hi,

do you take advantage of OpenExr format and your mia_exposure tonemapper ?

Have a look on that or post your settings of mia_exposure...

Greetz

Dominik

djltrain
09-11-2007, 09:05 PM
thanks! i will check that out and post results.

myself44
09-11-2007, 10:19 PM
Hi
Im been wondering how you guys apply mia_materials... because mines are soo ugly that it's better for me to use Maya materials.
So I did a interior scene (it might seems weird but I want to concentrate on the materials for now :P ). Almost every materials are mia, except some (like the floor and walls) are maya's.
So, I've seen in MrHoo scene the wood and metal are very very realistic, but when I try the Chrome or glossy metal material, it gives me something more like glass/mirror... even if I drag the reflectivity to like 0.2.
Im using the downloable mia presets pack and installing this pack, I've lost my initial mr "wood" and "metal" presets.
So could somone post up a mia_material for a normal "not vanished" wood and a normal metal (you know, like the legs of the table).

So, here's my render.. (notice, Im having trouble with lighting... again :P )
Well, ok, the bump floor is ugly (since I don't know how to apply bump to mia_m, I used a Blinn, btw MrHoo, can ya post the shading network of your ceramic floor if you dont minde of course)
I forgot to chagne the color of the right lamp pole,
the black table (right) should be glass, so I think I'll change "Solid glass" to "thin glass".
There seems to have some light issues where the wall and roof meets...
Tell me is there an influence on the render is the 'inner' and 'outer' walls have double-sided off ?
Anyway I appreciate your help guys :)
http://i14.photobucket.com/albums/a350/myself-44/interior001.jpg

MrHoo
09-12-2007, 09:37 AM
For now - I can only tell you for the ceramic floor tiles shader:
its in the downloadable scene i posted before.
So you can have a look on it freely :-)

About your other issues? Hm...
Your raytrace refl rays and fg rays are bumped up to 5 or so, I hope?

Dominik

myself44
09-12-2007, 09:59 PM
Well... I still have my old bug when opening downloaded scene, all mateirla are unknown and the render error "// Error: (Mayatomr.Shader) : mia_material14SG: no shader assigned in material"
still appear.
anyway, gotta try to figure out myself
thx for your help !

and yea my rays (raytrac and fg) are at 6.

the thing is that Ican't make realistic materials.. so hard

slipknot66
09-13-2007, 05:11 AM
Here is a test with MrHoo scene.
Area lights...FG (2 bounces)..GI
Some problems with one window.. where the light intensity is too much, but its easy to resolve.
The idea of using area lights is to create some contact shadows(not only with occlusion), also to bring some more natural interior light.But we need to be careful with overexposed areas.

MrHoo
09-13-2007, 06:37 AM
Hi slipknot66:

Great one!! I always had fear of using area lights, because my results were noisy and slow...

But I like your result! In my scene there is one problem with the right window (if you look on your picture), because the window frame has a little space to the wall... My modelling mistake :-(

Could you upload the scene, that I can have a look into ?

CU

Dominik

MrHoo
09-13-2007, 06:38 AM
Hi slipknot66:

Great one!! I always had fear of using area lights, because my results were noisy and slow...

But I like your result! In my scene there is one problem with the right window (if you look on your picture), because the window frame has a little space to the wall... My modelling mistake :-(

Could you upload the scene, that I can have a look into ?

CU

Dominik

**sorry - double post**

djltrain
09-18-2007, 03:05 PM
Where do you clean up the shadows in the sun/sky thingy. I have some majorly dirty shadows very grainy.PS Thanks MHoo for the advice eairly it helped tons!

djltrain
09-18-2007, 03:11 PM
never mind found it!

thanks anyway....

bwheels02
09-18-2007, 11:48 PM
Play with your FG ray settings, and throw a shadow transparency on the glass table so the light goes through it and creates the proper shadowing.

slipknot66
09-19-2007, 03:57 AM
Where do you clean up the shadows in the sun/sky thingy. I have some majorly dirty shadows very grainy.PS Thanks MHoo for the advice eairly it helped tons!
Go to Hypershade--Utilities--select the mia_physical sun node, go to samples.. there you can start with a value of 16 that im sure you resolve your problem.
Nice interior.You could use some area lights there :)

slipknot66
09-19-2007, 04:24 AM
Hi slipknot66:

Great one!! I always had fear of using area lights, because my results were noisy and slow...

But I like your result! In my scene there is one problem with the right window (if you look on your picture), because the window frame has a little space to the wall... My modelling mistake :-(

Could you upload the scene, that I can have a look into ?

CU

Dominik

MrHoo, i dont have access to the computer where i created your scene, as soon as i get to that computer i will post your scene back here.
Sorry for the delay answering you :)

djltrain
09-20-2007, 02:52 PM
Thanks SlipKnot66,

I found it pretty much right after i wrote that. Sometimes i get to dependent on these forums.

But now i do have a legit questions that i looked everywhere for but can not find anywhere. I am using IES for the Parabolics in that scene but anywhere i have glass it throws a huge burn out reflection of the point light that is used for the IES. Is there a way to turn lights reflections off?

I will post an example if needed?

Emil3d
09-25-2007, 07:10 PM
Hey guys, Iím glad to see nice test renderings and scenes being shared here. Thank you for your contribution. And sorry for the lack of reply on my side Ė Iíve been busy lately.

Iím also putting heavy test rendering activities on hold until I buy a faster computer, so that the play time is more fun and efficient. My current computer was due for replacement almost a year ago but I decided to get a new one after Maya has a version written for and tested on Vista with the latest hardware. I was able to afford this since I still do more 2D stuff but Iím gradually transitioning to 3D. Unfortunately Autodesk hasnít listed yet qualified hardware for Maya 2008 (http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=9683256) but I expect them to do so soon. Once I get a faster machine Iíll resume my tests. Meanwhile Iíll enjoy your participation and contributions here. Keep the good job up :thumbsup: and post your test rendering and scenes.

Emil3d
09-25-2007, 07:24 PM
i have been playing around with 8.5 for sometime now and still feel like a complete noop on the sun/sky thingy. How do you control the photons comming off of the sunlight? i get this all the time and have to add area lights to throw photons around the room but i like the look of just the sunlight. i have opend and used all the same settings as you guys and it just wont work

here is my stuff to look at if you could help that would be great!With interior scenes with light coming through windows from the physical sun & sky environment, I usually put the sunlight in the middle of the room, make sure that the light is not scaled, (to only display it larger, you can change its Locator Scale attribute in the Object Display section of the AE), let Mental ray calculates automatically the bounding box of the scene, and enable the automatic energy in the sun node. If the light is not facing the windows, I put a helper plane with its primary visibility turned off, outside the window in such position so that the photons shot from the sun direction bounce back into the room from the plane.

To be honest Iíve never been able to figure out how to control the focus of the photons with the bounding box values feature and thatís why I always use the default values of 0. Here is an example of the problem - I tried to visualize the bounding box effect with creating a dummy poly box without a shader parented to the light.

http://i111.photobucket.com/albums/n129/Emil3d/Photonboundingbox2.jpg


in the image above, the sun light is emitting photons with automatic energy and the Photon_bbox max values are equal to the size of the dummy box that encompasses one of the rooms. Following the help documentation I would expect that the photons will mostly land in the room within the bounding box, but as you can see the photon map visualizer shows thatís not the case. I increased the min values of the bbox more than a few numbers but MR did not store any photons. It stored photons when I made min = max values which gave a result identical to the default 0 producing equal distribution of photons on all rooms as shown in the image below.


http://i111.photobucket.com/albums/n129/Emil3d/Photonboundingbox.jpg


This is all what I can find in the help about it.

When photon_bbox_min and photon_bbox_max are left set to 0,0,0 the photon bounding box will be calculated automatically by the shader. If these are set, they define a bounding box in the coordinate system of the light within which photons are aimed. This can be used to "focus" GI photons on a particular area-of-interest. For example, if one has modelled a huge city as a backdrop, but is only rendering the interior of a room, mental ray will by default shoot photons over the entire city and maybe only a few will find their way into the room. With the photon_bbox_max and photon_bbox_min parameters one can focus the photon emission of the mia_physicalsun\ to only aim at the window in question, greatly speeding up and enhancing the quality of the interior rendering. Iím not smart enough:scream: to figure out this MR ďfeatureĒ, if someone understand how this works, please let me know.

Also I have no idea how to visualize or comprehend the difference of the min and max values after reading such explanation. In my imagination in the above example the min values when larger than 0 should cause a lack of photons (indirect light hole) in the middle of the room.

I had a chance to play with the portal light in Maya 2008 but not with its Emit Direct Photons feature enabled. However from the examples in the documentation it seems it works as a much better alternative to the Automatic Photon Energy options of the physical sun which is still available there and Iím not sure how and if it will work with a portal light.

MasterZap
09-26-2007, 11:56 AM
http://i111.photobucket.com/albums/n129/Emil3d/Photonboundingbox2.jpg


in the image above, the sun light is emitting photons with automatic energy and the Photon_bbox max values are equal to the size of the dummy box that encompasses one of the rooms. Following the help documentation I would expect that the photons will mostly land in the room within the bounding box

Here your expectation is wrong: Photons would be aimed at the dummy box, but they are not stored there (photons are not stored on their 1st interaction, because direct lighting takes care of that).

So the expected locations of photons is places where the photons would bounce when aimed at that box. Which is precicely what the photon distribution in your image suggests.

/Z

Emil3d
09-26-2007, 03:16 PM
Hey MasterZap, thank you for your help. I really appreciate it.

Actually Iím well aware that the photons are not stored after the first intersection and I expected to see photons inside the entire room encompassed by the bounding box in the same way shown in my second image from my previous post when the values of the bounding box were set to 0.

But hereís the funny thing, since I didnít save that experimental test scene, I tried to reproduce the problem again and after several tries I couldnít reproduce it. Now it is always working as expected. No matter what angles and even different bounding boxes I tried. As long as the bounding box covered the window the result was always as expected. This is the kind of result I expected to see in my first test.

http://i111.photobucket.com/albums/n129/Emil3d/bbox1.jpg

http://i111.photobucket.com/albums/n129/Emil3d/bbox2.jpg

You can clearly see the difference between these and the first image from my previous message. I feel so wired because Iíve been experiencing this problem on most of my tries and now all of a sudden luckily I canít reproduce it:). Ií hope it was some omission on my side but I canít imagine what I couldíve done wrongly so many times before and not doing it now. Iíve done stupid mistakes before but this one is kind of surreal. If I experience this again I will save and share the scene or my findings.

Anyway tank you for your help again. I also would love to hear from you a few words about the min values in the bbox and what their meaning is. Can I visualize them like I did for the max values with a dummy box. Leaving them at 0 seems to be OK but Iím curious in what cases one would change them.

Your help is always highly appreciated here:thumbsup:.

Kako
09-27-2007, 12:37 AM
Hi Emil3d.
That's a nice test setup to understand how the photon bounding box works.

The min and max values... Each of those numbers define a plane in a 3d coordinate system, giving us 6 planes in total. Each of these planes contain one face of our bounding box. So those values are not sizes, but coordinates that determine the bbox. The dimensions of the box can be calculated by maxCoordinate - minCoordinate.
So imagine that we have (0, 0, 0) for min values and (1, 1, 1) for max values. We'll have a unit cube that has a vertice sitting on the origin of the coordinate system.

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_000111.jpg

One more example: min=(0, 1, 1), max=(2, 2, 3). We'll have a 2x1x2 box.

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_011223.jpg

Now, imagine that this coordinate system is actually our light's coordinate system. In this situation, the light will be the origin:

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_lightsCoordinateS.jpg

Now we can see where the bounding box would be in relation to the light.
In the image above we're using the cube of our first example, where the min values were all zero. Thus, notice that the bounding box has a vertice sitting on the same position as our light. So it's important to see that if we just leave our min values at (0, 0, 0) (and considering we're not using automatic calculation of the bbox), the light WON'T be in the center of our bbox. If we want this to happen, the min values must be equal to MINUS the max values, for example, min=(-2, -2, -2) and max=(2, 2, 2).

That explains why you got that odd result with max=(23, 11, 21). In fact, the bounding box was something like this:
(Notice that there's a vertice on the same position of the light, since your min values were zero.)

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_EmilsError.jpg

A correct constrain of a dummy box to the light would be something like this:

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_correctConstrain.jpg

That's also the same unit cube of our first example. The important thing is that if our min values are all zero, then the box is contained within the >=0 semi-axes, as you can see in the picture above.

Some tests now. I'll use a scene like yours, but the hole in the cube will be on the ceiling instead. And let's use only one cube with the light at the center of the hole. I set the photon tracing limit to 1 reflection only to make it easier to diagnose the result.

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_01.jpg
http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_02.jpg
http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_03.jpg
http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_04.jpg

In the first three situations, as the bbox covers less of the hole, see how photons get a little bit more concentrated to that corner. The last image shows a uniform distribution of the photons. Notice that the min and max values are opposite in the x and y coordinates.

The z coordinate is not that important in our scene. Anyway...

http://img.photobucket.com/albums/v179/KakoCG/physicalSun_BBox_05.jpg

So... When you draw a dummy cube representing the bbox, that's actually a way of visualizing both the min and the max values.

Kako.

Emil3d
09-27-2007, 03:36 AM
Awesome explanation Kako:thumbsup:. If a simple illustration like one of yours was in the documentation, for me that would have cleared any questions about what those values mean.

In my opinion the creation of this metaphor and its explanation in the documentation is from and for scientifically thinking mindset. Unfortunately for people like me who are used more to life like experience metaphors this cannot be naturally understood without some aid like your explanations and illustrations.

Thanks god that this is not the case for most of the user interaction in Maya which is based on real life metaphors like for example: creating a cube in Maya is pretty much like in real life building a box in the middle of a room with a ruler that has only positive units of measure:).

Thank you for taking the time to put together all these excellent illustrations and clear explanation. You did a great job with this:thumbsup:

MasterZap
09-27-2007, 08:45 AM
Sorry guys for the crummy hard-to-decipher interface..... of course, all this was "supposed" to be hid away in a nice UI (like the "photon radius" aim tool in max) but the real world and priorities shifted that around..... besides, the "ideal solution" is to shoot sun photons only through the portal lights...... (.... maybe next version ...)

/Z

Emil3d
09-27-2007, 04:04 PM
Hey Master Zap, I really appreciate your concern.

In my opinion Autodesk should hire people with communication skills like scientific journalists who can quickly understand complex ideas and translate them to the masses in a more popular language pretty much like what Kako demonstrated with his excellent explanation and illustrations.

Geniuses like you should spend most of their time creating beautiful shaders and improving MR than writing manuals which you in most parts have done a very good job too:).

Kako
09-27-2007, 07:09 PM
Awesome explanation Kako:thumbsup:. If a simple illustration like one of yours was in the documentation, for me that would have cleared any questions about what those values mean.

In my opinion the creation of this metaphor and its explanation in the documentation is from and for scientifically thinking mindset. Unfortunately for people like me who are used more to life like experience metaphors this cannot be naturally understood without some aid like your explanations and illustrations.

Thanks god that this is not the case for most of the user interaction in Maya which is based on real life metaphors like for example: creating a cube in Maya is pretty much like in real life building a box in the middle of a room with a ruler that has only positive units of measure:).

Thank you for taking the time to put together all these excellent illustrations and clear explanation. You did a great job with this:thumbsup:

Thanks, Emilian! :thumbsup: It was worth it, then. I'm glad to help. But if you hadn't shared your tests in first place, I wouldn't have thought of writing those explanations. I see you're very committed to contributing to the forum and you too are doing a great job. Congrats for that!

Sorry guys for the crummy hard-to-decipher interface..... of course, all this was "supposed" to be hid away in a nice UI (like the "photon radius" aim tool in max) but the real world and priorities shifted that around..... besides, the "ideal solution" is to shoot sun photons only through the portal lights...... (.... maybe next version ...)

MasterZap, no need to be sorry. We know it's not your fault. In fact, the architectural shader's docs are maybe the best of maya's and mr's docs. And Emil3d pretty much said everything in his last post. We cannot thank you enough.

Kako.

djltrain
09-27-2007, 09:30 PM
Thanks for all the info guys! helping tons!

One thing you never see in 3d Viz work is interiors with no sunlight comming in. Just a space with (20) 2x4 parabolics and a lighting setup for that. I have tried multiple ways in this as well is there a good way to do it? I have done IES files but you can never get good bounce with those i have tried area lights in every parabolic to represent the lights it self. but then you dont get good lighting on the ceilings and stuff so i am open for a clean and good way to do this type of scene. I have looked at thousands of 3d viz projects and about 99.9% of them have sun light in them. So if you guys could help me with this one that would be great. :)

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