Billboard trees and shadows. Sun exclusion.

[Peter M. Gruhn]

I'm trying a system with two billboards. One set to face the camera and look like a tree; one set to face the sun and cast a shadow. Once I get it rigged right (disturbingly difficult for me) it works like a charm. Use the same alpha'd bitmap for both trees.

 

Except I have an issue I can't solve. In order to not have a stupid shadow on it, I turn off "Receive Shadows" on the visible tree. Except now it can't receive shadows from the rest of the scene. I'd solve this by creating a negative light with white shadows and settting exclusions correctly. Then I'd only need to exclude the shadow casting trees from the sun... pits, mrSun doesn't have exclusion.

 

For this rig to work, I need to have visible tree receive shadow (it might be around the corner on a building) but not cast. I need to have shadow tree cast shadow everywhere but on visible tree. I want to keep my mrSun for lighting the scene.

 

Ideas?

[Itoosoft]

You can use our plugin Forest Pack for this job. It includes a custom shader for Mental Ray that include many improvements for billboards, as self-shadowing fixing, improved illumination and more.

 

The free version of the plugin (Forest Lite) is available in our website (http://www.itoosoft.com).

Edited February 23, 2010 by Itoosoft

[Peter M. Gruhn]

Cool, I'll give it a try.