Vray Extra Attribute "Material Override" not working

[BeneZ]

Hello,

I was testing Vray Material Overrides.
Whichever material I plug into it, it hasn't any effect at all in rendering.

What could be the reason?
I created for test purposes a chrome material in Reflection slot
and a Material Wrapper (as a shadow catcher) in the shadow input.

I was expecting, that my material uses the properties of the other materials then.
Also setting the reflection slider high or low does not change it.

(Using VrayNext on IPR)

Thanks

[hermit.crab]

From the documentation:
"This group of attributes allows the material to be changed depending on the type of ray. For example, an object can be rendered with one material when looked directly from the camera's view, and with another material when viewed in reflections." I.e. setting a reflection material override will override how the material is seen in reflections, rather than overriding the base material's reflections.

[BeneZ]

So it is just exactly the same like the "Override Material"?
( https://docs.chaosgroup.com/display/...RayOverrideMtl )
I thought it can change the appearance of the primary visibility.

In particular I am looking for a solution to disable self-shadowing (self-occlusion) on a surface shader, but still maintain the ability to receive shadows from other objects.
Imagine this for use in 2.5D animation, where real pictures were textured on objects, and those objects should just receive shadows (imagine an space ship landing in a street scene), but not cast shadows on itself, because this would cause double shadowing.

Thanks for reply

[yolov]

Hi BeneZ

If it's acceptable that your object stops casting shadows completely (i.e. to not cast shadows on itself and other objects) than you can just turn off cast shadows in its render stats (or use a VRayObjectProperties node to do the same).
However, to make it only stop casting shadows on itself might be a bit more tricky, but it still should be possible with the V-Ray material override extra attributes.

See if this tutorials helps in some way: https://docs.chaosgroup.com/display/...pler+Info+Node

[BeneZ]

yolov
thanks, I was testing with the render stats,
but it is always casts self-shadows, see attachement with a test sphere

[SonyBoy]

I think you're confusing terminology. Shadow casting and the absence of lighting are two different things in CG, and a sphere will never "self shadow" by definition as it doesn't have any areas that can cast a shadow onto any other part of itself. Take a look at the two simple images, with an area of the sphere extruded and one render with cast shadows on, the other with it off. The overall direct lighting is not affected by shadow casting attributes at all. If you want completely diffuse shading (I *think* that's what you're looking for?), then either use a Diffuse render element, or apply a Maya surface shader or Vray light shader.

[BeneZ]

Hi SonyBoy,

maybe you are right. I misunderstand absence from lighting as kind of shadow

Indeed I am seeking an unlighted diffuse pass, but able to catch shadows on it.

The initial idea was trying to catch the isolated shadow on the object, which comes from other objects, in order to put this on a surface shader.
(also with Material Wrapper I couldn't isolate just the shadow)

Or in other words: I am trying to get a render pass, which only gives me the shadows, that were casted from other objects.
The intended usage is to get realistic shadow on a 2.5D environment from photogrammetry.

[SonyBoy]

I'm still not totally clear what you're looking for, but it sounds like your path of least resistance would be to get the result you want in comp. It's extremely easy to kick out a diffuse render element and a shadow element, which you can then combine in post to taste. I don't think there's any straightforward way to get a beauty render that includes totally diffuse shading on a shadow catching object.