Feather Pipeline and Occlusion Transp

[kensonuken]

I am trying to work on feathered chars and I need to calculate occlusion on top of it. I believe opacity maps can be used for the feathers but how about occlusion for these? do we need to multiply occlusion with Opacity maps? or is there anyway to calculate occlusion with transparency? I have very limited render power and short deadline. So i need something which can be fast enough but not using the classical ways of using dome of lights for occlusion on transp objects with dsm. Please suggest me a way..

[aracid]

Hey there

are u referring to ambient occlusion?

cause that can handle transparency

[kensonuken]

yeah Im thinking how to consider the transparency in while calculating the occlusion.... I mean in general occlusion doesnt take opacity maps ... But would like to know any way to consider opacity maps for occlusion...

[aracid]

yeah Im thinking how to consider the transparency in while calculating the occlusion.... I mean in general occlusion doesnt take opacity maps ... But would like to know any way to consider opacity maps for occlusion...

hey man

will this work for u ?

[kensonuken]

Isnt irradiance is more expensive than just AO?

[SpencerL]

Isnt irradiance is more expensive than just AO?

Unfortunately the Occlusion VOP does not have "Transparent Occlusion" as an option. But, the occlusion() vex function does. You can the set the sample filter argument to be "opacity".

vector occlusion(vector P, 
				vector N, 
				"samplefilter", "opacity")

Edited April 16, 2009 by SpencerL

[rendertan]

Hi I thought i could add some ideas, some time ago i found this "start to finish feathers solution" by Mark Newport, on the NCCA page, for a competing software package (Maya). It was comprised of a mel script to generate curves on a surface and animate them iirc, as well as a (renderman) procedural generator to generate the actual feathers, plus shaders for them and slim templates. There were a couple of nice videos as well, but can't seem to find them atm.

Thesis

User Guide

Feathers Solution code

NCCA Bournemouth has some interesting papers and occasionally code.

On the particular topic, occlusion for feathers, there was a thread at the 3delight forums a while ago about hair rendering, that had an occlusion implementation meant for hair/fur systems, by Luke Emrose, based on a paper by Ivan Neulander and Michiel van de Panne:

Rendering Generalized Cylinders with Paintstrokes

The particular post is here , post #6, perhaps it helps.

Edited April 16, 2009 by rendertan

[brianburke]

Hi kensonuken. I def. agree with SpencerL on the occlusion function.

One thing that tends to work really nicely with high frequency geometry like hair, feathers, plants, etc is baking. If you can bake down any of your occlusion calculations to textures or point clouds, you'll save yourself a lot of time in the render and prevent nasty flickering artifacts from the raytracing. I've found you can get away with baking occlusion even on deforming characters, because the direct illumination and coloration on the fur/feathers adds plenty of detail on top of the occlusion.

[kensonuken]

hey thanks alot guyz..