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spoondesigns
04-03-2003, 09:38 PM
Having problems with mental ray and creating volumetric light that peeks through holes. Easy to do in Maya renderer, but want to do it in Mental Ray. Does anyone have any tips?

Ken Koala
04-03-2003, 11:14 PM
Yeh
I have had the same probs as I needed to create an underwater scene using volumetric light for work. I couldnít seem to get shadows of objects in the volumetric density as well as the volume creating its own shadow..
Our tech guys (who need to learn to communicate better) mention specific volume shaders within Maya would do the job, which would be attached to the camera thus affecting any lights in the scene. I will do some research asap.

Ken

:beer:

CGA@UIW
04-04-2003, 01:48 AM
That'd be great! We're interested in this answer as well.

Thanks for your help.

stunndman
04-04-2003, 03:16 PM
could you give me an example of what you are looking for ?

some kind of fog ? in mental-ray called participating media ?

spoondesigns
04-04-2003, 04:06 PM
Imagine a wall with a volumetric light behind it. Say that there were bullet holes in the wall that we created by deleting polygons from the wall. The desired look is to have the volumetric light streaming in through the holes in the wall.

This is really easy in more 3D apps, but I'm just having a beast of a time with Mental Ray to get this effect to work.

Any ideas?

JupiterSunset
04-04-2003, 05:14 PM
http://www.motiondesign.biz

in the first tutorial there is one image that shows a volume fog;

check this.

good luck, tell us how you did it, if you succeed.



over

spoondesigns
04-04-2003, 06:46 PM
Perfect! Thanks for the link. I'll dissect this weekend and let y'all know what I find.

Thanks again!

X-Tender
04-04-2003, 09:28 PM
I try this tutorials some weeks ago .. and i find that it is very hard .. i never get the result like in the tutorial :cry:

spoondesigns
04-07-2003, 09:58 PM
Agreed...that tutorial is pretty well useless. They appear to have access to some magical Mental Ray shaders that I can't get for the life of me. Been playing with this more, but still no dice....so if there are any tutorials you know of, please let me know.

Thanks,
spoon

Ken Koala
04-08-2003, 12:56 AM
Guys

I had some spare time this morning to have a look at caustics via THAT tutorial. Everything is self explanatory besides what he does with the inner box????. Anyway tt took too long to render so I had to quit to continue with work work.

Spoon, all the shaders that are called for are generic MR shaders that are accessible if you have installed MR correctly. Check your environment variables. You should be able to access all the my shaders via the hypershade etc.

'Still no dice' as spoon said.

Fella's, also try getting your hands on a book called 'Rendering with Mental Ray, pub by SpringerWienNewYork and writen by Th. Driemeyer. This explains ray marching etc.

Still pluggen away

Ken

:beer:

stunndman
04-08-2003, 01:13 AM
Everything is self explanatory besides what he does with the inner box????.

i don't have the tutorial at hand but i think the inner box is the actual volume - it has a parti_volume and a parti_volume_photon shader attached to it and just within this volume any participating media effects will show up

using the parti_volume node is really easy - just create a box - assign a parti_volume node to the volume shader tab of your shading group - link a light's message attribute to the lights attribute of the parti_volume node and that's it - light rays from the linked light passing through the box (oh yeah, assign a transmat material to the surface shader - again in the shading group tab in the mental-ray section) will now call the volume shader, et voilŗ

i can set up a little tutorial if anybody has troubles with this

Ken Koala
04-08-2003, 03:46 AM
Thanks heaps mate

I thought that the outside box was the bounding box for the volume? Anyway same sh#t same smell.

A tutorial would be of great use digger. Iím sure all of us would really appreciate it.
I dont realy have spare time to figure this out. I get beaten over the back of the head even if i turn sideways. Time to move on.

Thanks Stunndman.
Peace out

Ken
:beer:

spoondesigns
04-08-2003, 04:27 PM
Originally posted by Ken Koala
Guys


Spoon, all the shaders that are called for are generic MR shaders that are accessible if you have installed MR correctly. Check your environment variables. You should be able to access all the my shaders via the hypershade etc.


:beer:

Thanks for looking at that. I appreciate it. I have been trying to get those MR Shaders set up. How to you check your environment variables? I know that they list this in the Mental Ray documentation, but I'm just not finding it.

Thanks for your help.

spoon

spoondesigns
04-08-2003, 04:36 PM
Originally posted by stunndman
i can set up a little tutorial if anybody has troubles with this

That would be fantastic if you would....I'd praise your name until the day I died.

spoon

spoondesigns
04-08-2003, 06:57 PM
OK...here's what I've found so far....

1) The way to set a new environmental variable is to go to your Maya.env file (mine was at C:\Documents and Settings\spoon\My Documents\maya\4.5).
- Open the Maya.env file with Notepad
- enter the following line:
MAYA_MRFM_SHOW_CUSTOM_SHADERS = 1
-this will allow you to at least see the mental ray shaders in the Hypershade and when you attempt to add new Render Nodes.

Still haven't figured the rest of it out. I've got a box with a LambertSG and have been able to place the parti_volume into the Mental Ray - Volume Shader section. But I still have not figured out how to get the light in the box to 'see' this parti-volume shader - so still not volumetric light.....but small steps.....

Ronald
04-09-2003, 08:18 PM
i tried that one (and it works), but the problem seems to be, that you can't light anything with those lights within the participating volume geometry and the do not cast shadows. any resolution to that? by the way - you can do a little workaround for the normal volumelight that come with maya: to get rid of the strange intersections when two volumelight cross, you can turn up the spread of the volume to 2 (standard is 1). this will make it better.
and for the light through hole trick, just override and boost up the volumesamples of the volume! take forever to render but it work (also with the maya renderer when using raytraced shadows)!


Ronny

Ken Koala
04-10-2003, 02:38 AM
Originally posted by Ronald
you can do a little workaround for the normal volumelight that come with maya: to get rid of the strange intersections when two volumelight cross, you can turn up the spread of the volume to 2 (standard is 1). this will make it better.


Yeh, thatís a piece of piss mate.
My concerns are totally related to mentelray and volumetric light within caustics. I just need some extra time in the day so I can work this out.


Originally posted by stunndman
i can set up a little tutorial if anybody has troubles with this


As I said earlier, this would be greatly appreciated mate.

Ken
:beer: :beer:

Ken Koala
04-10-2003, 03:02 AM
I must apologise
I read back what I just wrote which seemed to sound aggressive towards Ronald. Please donít take offence mate.

Ken

Ronald
04-10-2003, 08:14 AM
no problem man, i just wasn't replying to your post but to the original topic. thought this would be of interest for all!

Ronny

stunndman
04-10-2003, 08:33 AM
Originally posted by Ken Koala

As I said earlier, this would be greatly appreciated mate.


it's almost done and as soon as i find some peace i'll put it up

basically i already described the full procedure above and the tutorial won't tell you much new - the key is to connect your light's message attribute (it's hidden by default in the connection editor) to the parti_volume's lights attribute

i'll post the link here as soon as i'm done

Waters
04-21-2003, 09:41 PM
ya, lets get a short tutorial, and a few images.. thatd kick ass :thumbsup:

xyz
04-22-2003, 02:49 PM
Hi guys, the volume caustic tut is perfectly well reproducable, I repeated the steps just after the tut came out.
The problem but remains, that I could not figure out the correspondence between mr base shaders structure and the build-in shaders which are the render network blocks in softimage environment.
The point is that in maya and in xsi the mr shaders are introduced differently: in maya the mib_base (mental image base) shader nodes are subjects to build a shader network, and it turns out not to be so clear to do. In sofimage people operate rather the more known things like "blinn", "volume fog", "texture marble" and so forth, do not borrowing theirself with the core mib_shadings underworld. And the rules of that mib_shaders network building under clicking a buttons in Render shelf interface is the those sacral knowledges to may help understanding mr use in maya. If someone drag me a resourse to look at, I would be of great attitude.
As to ligth beams through the holes in smoky room scene, I made it tousand times working in SI 3D prior to maya with use of mental ray. As a matter of fact, this can be done in two ways. One is the precise and slow way, the one you try to work out - to declare the space were the smoke is to may appear by using some dummy bounding object with march fractal volume shader assigned and so forth, but I almost always used mach simplear method with great control, by use of "bionic light" and "bionic volume" shaders together assigned to spot light. Starting from SI 3.7sp1 or 2 I guess there were FX director interface introduced to turn this on for selected light by two mouse clicks with nice "shards" control. (But in this case the intersection of two volume spots do happen rather not correctly)
I looked in xsi to check which way it happens there and found vary same stage. This bionic light stuff (the main code stills unchanged since middle 90-ths) are related to so called "fast_volume_effects", as a shader preset, or button from Render shelf "Get_Property_Volumic" applide to spots works as well. Fast and easy.
But how to make it in maya? The section of "usind custom mr shaders" says close to nothing since mean "mr base shaders" and they are obviosly used to translate the maya shading network with.
How to use a shaders from SI shader library whose file extantions are optional? Is there a way to translate a xsi shader presets to something readable? Could anyone lit some ligth in this area?

xyz
04-22-2003, 04:23 PM
Just realised that DGS - diffuse, glossy, specular! (reading the highend3d forums). And those DGS mr shaders are to deal with "physicly correct" something. Funny thing, I made a search in mayatomr doc for DGS .... silense.
From highend3d forum souns that all DGS stuff works with huge wirdness. Where is the DGS paradigm is vocalized clearly? What is the explanation of that particular membership of "Create Mentar Ray Nodes" tab?
Sounds quite stupid to verbilize such a questions, the doc files are the optional way if not explane, but declare names at last, as I mistakenly believed.

Ozren
04-23-2003, 09:14 AM
Maya has some serious problems with fog. I managed to make fog the normal way Maya does with its own renderer.

Create spot light, attach for to it. Now, set Intensity to 5, Density to 9, and Volume samples overide = 30 (click light, in tabs find cone shape, renderstats). In Mray turn on RT, and also turn on RT in light. You should get something like i did, so fog works, and gobo effect is there, but there are some serious problems going on here.

First of all, dont turn Area light on, you will get a black hole, and you will have to delete your light to set the fog again, because once you render with Area light, you will always get that black hole, sometimes not. If you try to twek the light, most probably you will end up with some strange effect or something.

If you turn GI, FG, or anything else, you will end up with black hole again (black fog). Still trying to figure out DGS lights as i hope they will fix the problem.

I hope i helped someone.

Throbberwocky
03-04-2004, 07:41 PM
I just wondered if the tutorial by stunndman is already available?

johnnynightlife
03-24-2004, 05:28 AM
has anyone seen that tutorial yet? I've been trying to implement light fog into my present scene, but got poor results:hmm:

BLee
03-26-2004, 08:09 PM
Hi all,
Seem like look similler to my problem too. could anyone tell me how??


click here : Same problem with volume light. (http://www.cgtalk.com/showthread.php?s=&threadid=133391)

Throbberwocky
03-26-2004, 08:33 PM
Check out this thread: http://www.cgtalk.com/showthread.php?s=&threadid=131608

Geeves
03-26-2004, 10:33 PM
I'm having similar problems with my scene. Hopefully someone out there has some answers. I've tried several things with mixed results and ended up with way more questions than answers.

Here's a photo of what I'm going for...
http://www.concentricvibrations.com/NewFolder/burma-monks-cooking.bmp
...And here's the best render I have so far...
[http://www.concentricvibrations.com/NewFolder/volumicTEST.jpg
Here are my questions...
1. Can anyone tell me how I can soften the fog particles down to make it look more like my reference?

2. Ultimately I am hoping to render this with Mental Ray using Global Illumination and FinalGather, but I have yet to even get the volumetric rays to show up. Can anyone give me some advice on how to set this up?

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