Sunday, January 31, 2010

Volume Light Rendering

So I took a slight detour from my rendering plans. I dived into volume lights instead of writing that Blinn shader. I initially thought that it would be easy, but it really was not. I had a lot to understand about how the different shaders work together to make this work. In most other 3d programs my experience is that the volume light is a function of the light. However in 3delight this is not the case. It's a bit more cumbersome but I can sort of see why you would want to do it this way for one important reason, it's a volume in space and you can limit it much better and have more control over it, if it's separate. But the work flow to make it works like this:

1. Make  a scene with a back wall and put something in front of it.
2. Make a light that cast a deep shadow.
3. Make another object, give it some geo properties so it is transparent, assign and interior smoke shader to it.
4. Make sure the volume object is bigger than your back wall.
5. Turn on all the check boxes in the shadow map section in renderglobals

So yeah a convoluted, but worth it. No I just have to see about making it render faster because I'm sure my settings are not good. Time to look in to that step size parameter.

Saturday, January 30, 2010

Soft area shadows from a single shadow map

I knew you could create soft shadows from mulitple shadow maps and doing some averaging to blend them into a single soft shadow. But I didnt know you could do it with only a single shadow map. But Bertrand Bry-Marfing found a way and put the shader up on his site:

So now I've been able to compile the shader and use it in maya with 3delight. I was going to try for something like this after I got the occlusion stuff to work but since he had the shader already I figured I could give it a go. It also works with deep shadowmaps !

Thursday, January 28, 2010

I wrote a point cloud!

I rendered out a point cloud from maya! I know! Exciting! So know I just have to make a shader that uses that to make an occlusion pass and I've succeded in step one of my renderman goals.

My next step is to create a blinn shader that willl bake out it's own lighting and shading into the point cloud so I can use that to start doing some fake GI bounces. This is all very exciting to me. I'm so used to ray tracing everything and having to worry about fitting things in to memory but now I will not really have to worry so much about that. I'll be able to render trees and grass and still have occlusion and some form of GI color bleeding, very fun. I should write a tutorial up soon.

Monday, January 25, 2010

3delight Passes

Point Based Lighting very much interest me right now. As a Vray user I love it's fast raytracing which is really nice for setup and let the processors chew on it kind of stuff like we do at work. Raytracing car reflections is the best and fastest way to get jobs done. But when it comes to doing pretty much anything else, I'm all about the quick and good. Renderman seems to provide that. The only trick is you have to understand how to make it quick.

So I've got to the point where I understand that I need to make a pass that bakes out a point cloud for me to. This should be a pre-pass like a shadow map but it doesnt need to happen all the time but should be automatic enough so when I change a scene I can easily update it.

Now comes the tricky part. Using the point cloud to shade. I've seen examples as a surface shader and as a volume shader. But from how I think it should work, it should be a light shader to cast the fake GI back into the scene. Then it can be a AOV of it's own and separate from the shader calls for surfaces. But I'm not sure if that's how the volume shader works.

But my big curiosity is how you can shade the points in the point cloud with the surfaces on the object for color bleeding. Since I'm so new to this I think I see the code to do it but dont really understand it.

I think by the end of this weekend I need to make my own surface shader ( preferably with Fresnel fall of in reflection and spec with a gloss setting) and be able to make a point file and use it to make an occlusion pass.I'll have to learn about what 3delight calls sets to be able to make all that work.

Saturday, January 23, 2010

3delight begins

I'm finally taking the plunge and learing how to render in 3delight. I'm choosing 3delight over Prman primarly because it's cheaper ( and the first license is free). I also like the intergration better.

Pixar's artist tools are a bit too artist friendly for me. Every time I have messed around with them I seem to get more confused about what's going on. They tend to hide things and make things work without me understanding how they work. In my book thats a big no no. Becasue if something doesnt work I need to make it work.

They also have a shave and a hair cut workflow that I'm interested in. Hair, fur and grass are all things I would like to be able to render better and unfourtantly raytracers are not able to do those effects quickly.

It also allows me to use python in maya. Python is everywhere except for my main 3d package at work (3d max) so I'm going to be able to test the waters with out having to install and cobble together the blur python package for max, that I could never get to work at home. But that was just my experience.