CGTalk - Clip maps in XSI?

Leftover

03-28-2003, 11:56 PM

How to build render tree network for simulating "Clip maps"? Could anyone help?...

"Clip map" is Lightwave term. It's similar to transparency map, exept it doesn't have gradations of grey and uses just black and white colors to key out parts of geometry (so you don't have care about specular channel as well as IOR if object has refractive parts) ... major difference between transparency and clip maps that Shadow maps take Clip map into account....

I have been experimenting with render tree but had no luck.. so far....

Is it even possible with XSI?

Atyss

03-29-2003, 02:04 AM

Plug your texture into the color1 input of a Mix_2colors node, and then plug your "clip map" into the Weight1 input of the Mix_2colors node.
In the Mix_2colors node, set the mode to Alpha.

Finally, connect the Mix_2colors node into the diffuse input of the surface shader.

Hope this helps
Salutations - Cheers
Bernard Lebel

tachy0n

03-29-2003, 04:07 PM

Also if you are planning to render out a large amount of billboards (ie planes or such with clip maps) to simulate stuff like trees etc, then check out the 'sprite' surface shader type: Nodes->Illum->Sprite in the render tree. This is optimised just for usage of this sort.

Leftover

03-29-2003, 04:27 PM

Thanx for replies!

Yes! Stencil is what i need :)
Exept one thing... shadow maps just ignore matte map...

Atyss

03-29-2003, 06:23 PM

Originally posted by Leftover
Thanx for replies!

Yes! Stencil is what i need :)
Exept one thing... shadow maps just ignore matte map...

That's an inherent of behavior of shadow maps, no matter the renderer. You have to live with it.

One thing you can do is to make your planes not cast shadows, and create a light with a projector. This projector would be a grayscale image that simulates the shadow of a tree. You could duplicate this light a couple of times to add these faked shadows in your scene.

Hope this helps
Salutations - Cheers
Bernard Lebel

Leftover

03-29-2003, 07:56 PM

Well in LW clip maps work with shadow maps.
Though for XSI it doesn't matter probably.. it renders shadowmaps as long as arealight shadows almost... it's more critical for LW because shadowmaps there are lightning fast...

Light projection won't work in my case... because i need to reveal number of complex objects (which contain many different materials including refractive/reflective ones) using animated "clip map". These semi-revealed pars should cast shadows onto each other... and so on.... it's sort of specific task...

Thanks for tips and suggestions.. it was really useful :)

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