View Full Version : Transperancy Maps in Shadow Pass

02 February 2009, 07:29 PM
I have a background set loaded with transparency maps. I really need to have a shadow pass that can cast shadows through the tranny maps, and not just treat them like planes (which obviously cast rectangular shadows).

Is there a work around for this? People must come across this all the time.

Btw, I am using XSI 6.5.

Please help.

Thank you,

02 February 2009, 07:32 PM
Post a screeny of the rendertree for one of the objects. There's many ways that transparency maps can be used, so if I see an example of the setup you're facing I can probably recommend some options.

EDIT: On the chance that it's the most simple of setups, simply make a new Empty Pass, on the Objects Partition add an Override on the Surface port of the Materials. Plug a Shadow Shader in to that. Now the shadows will be cast into an Alpha Channel. If you want them to be in the RGB space as well, simply enable the RGB option in the Shadow shader's options.

02 February 2009, 07:44 PM
thanks JDex for the quick reply. I am using a mac so frustratingly I can't do a printscreen screen capture.

I will try my best to explain.

I have a bunch of cards in the scene (grids) of grass for example. The texture has an alpha channel that is acting as the transperancy map. The texture is plugged into the transparency of each grind and using the alpha for the transparency map.

What I would like is to be able to have a shadow pass that casts shadows of the blades of grass (as an example) onto the ground as opposed to it looking as a flat plane.

Is there a way for the shadow pass to use the transparency maps from individual objects?

02 February 2009, 07:48 PM
See the EDIT I just finished in the previous post. Try that out, and we'll go from there (though I may be a bit delayed as I'm headed to work shortly and will have no XSI to reference).

02 February 2009, 07:50 PM
thanks, I'll give it a try!

02 February 2009, 09:36 PM
Did that do it for you?

02 February 2009, 11:17 PM
I think that will work on an object per object basis, but the problem is we have so many transparency maps throughout the environment that it would be hard to apply this to every object in the scene.

Is there an approach that can cover it for a whole partition of objects with different transparency maps scattered throughout the scene?

Thanks again for your help.

02 February 2009, 11:46 PM
Actually the steps I listed should cover every object in the Partition.

The Override is applied to the partition. When you "override" the Surface port of one of the objects in the partition, all objects in the partition should be effected in the same way.

CGTalk Moderation
02 February 2009, 11:46 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.