No soft shadows through translucent materials?

[R Reynolds]

My setup is simple. I have a small klieg spot pointed at the top of a vertical cylinder. Beyond the cylinder is a small flat screen with its translucent attribute = 50%.

 

When the camera is to the right of the cylinder and views the screen you can see both the shape of the spot and the cylinder's shadow being cast on it. The same is true when the camera is to the left of the cylinder and viewing the other side of the screen but these shadows are now being transmitted through the translucent screen.

This short video shows a 9 pass progressive screen render as you view the screen from the right and then from the left.

As you can see, the front facing soft shadows are correct but the shadows supposedly going through the translucent material  only have sharp edges.

Is this a real render glitch or have I missed a variable/check box that needs attention?

 

[robcat2075]

Is that a z-buffered or a ray-traced light?

[R Reynolds]

Klieg set to 

Cast Shadows

Raytraced

rays cast 4

Distribute in passes OFF

Bias 0.02"

Darkness 80%

 

But I tested it and Z buffered shadows exhibit similar behavior.

[robcat2075]

Yup, I think that is a render error.

Can you post the test case?

[R Reynolds]

See attached project.

translucent_test_embed.prj