Mental Ray skills test scenes

[Emil3d]

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]

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]

Hey guys

I uploaded my scene as test scene at rapidshare:

LINK

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]

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]

…and an update…

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

what do you think?

Cheers

Dominik

[MrHoo]

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]

thanks! i will check that out and post results.

[myself44]

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 ). 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 )
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

[MrHoo]

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]

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]

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]

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]

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]

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]

never mind found it!

thanks anyway…

[bwheels02]

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]

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]

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]

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]

Hey guys, I’m 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 – I’ve been busy lately.

I’m 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 I’m gradually transitioning to 3D. Unfortunately Autodesk hasn’t listed yet qualified hardware for Maya 2008 but I expect them to do so soon. Once I get a faster machine I’ll resume my tests. Meanwhile I’ll enjoy your participation and contributions here. Keep the good job up and post your test rendering and scenes.