Problem with the materialID pass

[Scyla]

Ahem, sorry for double posting but it seams that the first thread on this topic was posted in the wrong forum by me and I'm sorry for that but I still need urgent help. So sorry for posting it again. This time hopefully in the right forum!

Anyway,

I have a problem with the materialID pass of vray.
If the material is semi-transparent, the area were this material is applied ist also semi transparent in the materialIDPass thus the materialID colors of the objects that lie behind this semi-transparent objects are visible.

This results in the problem that you can't determine the the material of the object because the color is wrong (it's mix with the materialID color of the object behind this one i.e. the actual materialID color is yellow and the materialID color of the object behind is blue so the color appears green) .

I'm working with the standalone renderer of vray and enabled the materialID pass in a .vrscene file via.

RenderChannelColor vrayRE_Material_ID {
  name="materialID";
  alias=115;
  consider_for_aa=0;
}

Unfortunately I cant post you any images so I would be glad if you can help me without demanding an image.

Thanks in advance!

[Scyla]

I guess I found the problem myself.

The issue comes form a material that I created

I use

Dummy transparency_0_790 {
  change=AColor(0.67, 0.67, 0.67, 1.0);
}

to change the transparency of the material.
The plugin is used here.

BRDFDiffuse diffuse_component_0_790 {
  color=Color(0, 0, 0); 
  color_tex=diffuse_texFresnel_0_790;
  transparency_tex=transparency_0_790.change;
  roughness=0;
  use_irradiance_map=1;
}

In the original Version I exported from maya the section looked like this

TexAColorOp ShellTexture_2 {
  color_a=AColor(0.67, 0.67, 0.67, 1.0);
  mult_a=0;
}

BRDFDiffuse diffuse_component_0_790 {
  color=Color(0, 0, 0); 
  color_tex=diffuse_texFresnel_0_790;
  transparency_tex=ShellTexture;
  roughness=0;
  use_irradiance_map=1;
}

So there has to be the problem because with all other semi-transparent materials the material ID is displayed correctly.

[vlado]

The "mult_a" parameter of the ShellTexture_2 texture is zero; this means that the result from the entire texture is zero and your material is not transparent at all - which is probably why it's working with the material ID.

In any case, there is no good solution for this problem other than using easily separable colors for the material IDs (e.g. pure red, green, blue), or disabling the filtering for the material ID element.

Best regards,
Vlado