V-Ray Dirt's Invert Normal option still affects crevices

[1funk]

The manual states that v-ray dirt's "invert normal" option should not shade crevices, but this isn't working correctly.

https://docs.chaosgroup.com/display/...y+Dirt+Texture

"When disabled, the rays are traced outside the surface, and when enabled the rays are traced inside the surface. This means the effect can be reversed with respect to surface normals. For example, when this option is enabled, open corners (and not crevices) will be shaded with the occluded color"

[1funk]

I have discovered that "invert normals" actually works correctly, if your mesh does not contain intersecting parts. In my image above, I have several separate cube meshes intersecting eachother.

If I boolean the meshes together to make it a single watertight mesh, then the invert option does not shade the crevices.

It would be nice if an option could be added to make it work with intersecting geometry (like rounded edges on the vray material)

[1funk]

I created an image to illustrate the issue a little clearer

[1funk]

I'm just following up on this thread. Does anyone know if dirt works correctly with separate intersecting meshes in Next?

[Muhammed_Hamed]

Same behavior still exists in Next..
Grant Warwick talked about this issue in his procedural shading webinars, the current behavior with invert normals on is not correct

[vladimir.nedev]

I am not sure this could be fixed to work "correctly". We should maybe modify the docs not to mention crevices explicitly.

All the "invert normals" option does is fire the AO rays inside the hit surface.

If there is an object there, it will generate occlusion.

In your scene, you could enable "Consider same object only", and maybe you will get a result closer to what you expect.

Greetings,
Vladimir Nedev

[1funk]

vladimir.nedev "consider same object only" doesnt make any difference in this case, because all the geometry is in the same item. It works if I put each "box" in it's own item though, but I'd need to test it out more.

When I initially did this test, I was comparing to modo's occlusion texture which has concavity/convexity options which allow you to get the "correct" look with intersecting meshes.

Octane's dirt texture actually works more like V-ray's, but doesnt have a "consider same object" option.

[vladimir.nedev]

consider same object only" doesnt make any difference in this case, because all the geometry is in the same item. It works if I put each "box" in it's own item though, but I'd need to test it out more.

Oh, yes, of course, didn't think about that.

We could have an option to ignore front face hits (or back face hits), then maybe it will work more like Modo's concavity option.

Greetings,
Vladimir Nedev