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Mantra Specular -> Arnold Specular = valid conversion

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Hi. I`m writing bridge between maya and houdini. At now i experiment with export mantra surface to arnold aiStandard material. It use user-base rules to accurate export materials from houdini

All works fine but i dont understand how to correct translate specular roughness from mantra surface.

1. In mantra surface it is specular angle

2. In arnold aiStandard - specular roughness

3. Also arnold has two BRDF models - cook_torrance and ward_duler (with anisotropy and rotation attributes)

4. As you can see in export code it is remap(shop_node.evalParm('spec_angle'),0.0,90.0,0.0,1.0) ). remap is simple function to fit new range (0,90 -> 0.0,1.0 in this example)

5. Renders with specular angle=10 are diffrent

6. So, how to translate specular angle to specular roughness ?



Edited by Alexey Vanzhula
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