Light shadow not respecting transparency

#1


Scene is simple, only 3 objects.
EyeLashes object apply this material

When there is no light in scene, render looks okay
But when I add a light to the scene, light shadow seems can’t recognize transparenct object, it doesn’t respect transparency map, still consider EyeLashes object is a opaque object, and cast incorrect shadow.

How can I fix this?

#2

I did some digging, and I found something.
I am using Maya 2018 and V-Ray 3.60.03.
In the first post, EyeLashes object applied a phong material, this may not be supported very well in V-Ray, So I apply a VrayMtl instead.

Obviously, transparency need to be inverted.
So I add a reverse node.

EyeLashes object itself looks okay, but shadow just not right, just like the first post.
reverse node is not the only way to flip transparency, there are others way, like remapColor node.


Now everything looks decent.
There are still some methods to flip transparency.
Such as:

  1. Adjust EyeLashes texture map file node, set Alpha Gain to -1 and Alpha Offset to 1
  2. V-Ray has a colorCorrection node, that one can flip transparency too

And all these methods won’t cause shadow problem, only reverse node does.
So I am curious, what happen?
reverse node is bugged or I can’t use it correctly?

#3

Instead of using the Reverse node, you can just fix your Cutout Opacity texture file.