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ezekiel66
08-24-2007, 03:06 PM
I'm in the process of creating the displacement map for the roof of a house. I've uploaded an image here:

http://img508.imageshack.us/img508/8605/displacementaa1.jpg

(rendered with mental ray)

The roof is one single polygonal object with UV-mapping applied. The main problem now is (as you can see on the image at the spots circled in red) that the roof sort of 'explodes' when the displacement map is applied.

It looks like the shingles were seperate planes when in fact the roof is one single solid object, the part of the object that is being displaced by the displacement map sort of detaches from the rest of the object.

Is there some way to resolve this?

noobman
08-24-2007, 05:19 PM
I have the exact same problem. In my model, the corners of the structure appeared to have been separated. I think this has something to do with the displacement map. Does maya read 50% grey as the neutral value? or does it start with white?

Kako
08-24-2007, 08:26 PM
Does maya read 50% grey as the neutral value? or does it start with white?
Nope. Zero (black) is neutral in mental ray displacements. That's why if you simply attach a texture without changing the range of it's values, only positive values will be used and you'll only get displacements in the normal direction.
If you want 50% grey to be the neutral valeu, you have to shift the values of your texture half way down. One way to do it is setting the alpha offset of your textures to minus half the value of the alpha gain. Or you can use a Set Range shader.

To ezekiel66.
You can apply this displacement to a separate plane, or try to put a thin stroke with a neutral value running along the perimeter of your UV map.

Kako.

ezekiel66
08-27-2007, 10:23 AM
Thanks Kako!

I have a different question now: The idea is to use one displacement map for the shindles and a different one for the snow.

I tried to create two blinn materials in Hypershade, assign a displacement map to each of them, then create a layered shader and assign those two blinn materials to the layered shader.

Unfortunately the two displacement maps seem to have been lost in the process. Is it even possible to assign two different displacement maps to one shader/ one object in a scene? How would I do that?

cpan
08-27-2007, 10:55 AM
that's because you actualy plug the materials into the layered shader
thus their own SGs (wich contain the displacement) are ignored.
you need to plug a displacement into the layered shader SG
and further the two textures layered into the displacement.


texture1 -->
layeredTexture --> displacementNode -->
texture2 -->
layeredSG
material1 -->
layeredShader -->
material2 -->

Kako
08-27-2007, 03:42 PM
And you can also use a ctrl_multidisplacement shader.
http://www.mymentalray.com/mymr_shaders/shaders.htm
You can find it under the special shaders. And there's a tutorial about it in the tutorials page.

Kako.

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