Blacks in Refraction

[Khazmadu]

I have a few problems with black areas in Refractive Objects. To isolate the problem did I make a realy simple Scene.

2 Spheres. One as Enviroment one as Object.

Envioment Sphere: Only visible for refraction with a white iluminating Shader.

Object Sphere: Shader with everything turned of except refractions.


I hope it's understandable what I mean. You can download my test Scene here:

https://www.dropbox.com/s/taylnnx70i...roblem.mb?dl=1

I do Expect a Render of of a Completly White Sphere. But I get this:




Where is this Black Coming From?

I can Turn on the visibility for Reflections. In that case the Sphere renders completly White but that wouldn't be what I want.
It also doesn't make sence to me because the Shader do not have any Reflection Attributes Activated.

I'm using Vray 3.10.01 with Maya 14/16

[ivaylo.ivanov]

The balck areas are because you have turned off "visible in reflection", so if a ray happens to reflect inside the sphere, it directly returns black.

[tashko.zashev]

Hi,

The "black" parts over the Sphere are actually reflective rays hit the environment (some of the rays gets reflected from the inner surface due to the wide hit angle and IOR of the material. ), since the Sphere (the environment one) has Visible in reflection parameter unchecked. There is no bug here it's just designed to work that way.

What you can do is to add another Env. Sphere and have separate control of that area or just use the refraction environment color/texture parameter.

[Khazmadu]

Thanks for the answers.

It seem's right that the black areas are reflected ray's from the Inside. That also explains why I had a lot less problems with double sided objects.
Shouldn't the ray from the internal reflection convert to a refraction ray if it extis the object?


Using an enviroment override is a good idea. I will use that.

[tashko.zashev]

Shouldn't the ray from the internal reflection convert to a refraction ray if it extis the object?

Actually I'm don't know if this is feasible, have to ask our Dev. team about that.