Digital Arts Front :: Forum - Weird shadows and glass (mental ray)

Forum Index - Lighting - Weird shadows and glass (mental ray)

There are 6 replies to this topic

-fredriku
Junior Member

2 years ago

I'm trying to make a render with mental ray using "ProMaterials: Solid Glass", however, when shadows are "ON" on my lights i get weird rectangular artifacts.

See this setup: [Link to www.astud.chalmers.se]

The issue seems to resolve if i place another object with the same material in the scene

[Link to www.astud.chalmers.se]

But it seems to make a difference on WHERE i place these objects, they must be fairly coplanar or far off otherwise the issue just worsens

[Link to www.astud.chalmers.se]

Anyone have any idea on why this is happening? It took me like 20000 years to figure out the workaround but it really bugs me. I'm using the "raytrace shadow map" for the lights, as soon as i change the shadow map to anything else the glass either looses its translucency or the material cease to transmit light through it.

At first i thought it only had something to do with the shadow maps, cause the rectangular shadows disappear when i turn shadows "OFF", but since they also disappear when i add other objects (depending on WHERE i put them).

This feels like a bug to me

The scene is also fairly small, millimeters for units and 1,00 millimeter/unit in the unit setup, I have sometimes noticed that the world scale might affect render behaviour, but it shouldn't behave like this IMHO.

Thanks in advance!

-Tyson
Senior Member

2 years ago

Try adding some detail to the mesh. I havent used these pro materials before but I set up the same scene you described and got the same result. when I added cap segments to the cylinder the shadow artifacts were gone.

-fredriku
Junior Member

2 years ago

Thanks for the help! Do you know why this happens and disappears when adding detail the cap segments? I'm not satisfied by just watching a clock tick I wanna know why it does

-Tyson
Senior Member

2 years ago

I guess the shader is dependant on the mesh topology to some degree. Like its thickness for example would effect the refraction. I'm not sure why in technical terms. I read the max reference on the shader and it doesnt mention anything much. I'd need to find a more detailed manual on the po materials I guess.