[Cycles] Hair object transparent shader from texture alpha being blacked out

I have getting the following render:

This is the object that is being instanced. The trees that are more solid do not exhibit this behavior in any fashion)

This is with Shadow ray visiblity disabled for this hair object. With Shadow ray visibility enabled or with branches being darkened, the blackened out areas increase.

What appears to be happening is in some instances:

  1. Sampling at a higher rate does not improve the darkened portions.
  2. As you can see, the darkened portions are sharp edges that correspond to the entirety of a billboard plane.
  3. Portions of a billboard that is in sufficient shadow, limited visibility and/or at a particular angle, is rendered as entirely darkened instead of having the alpha of the texture mixed correctly with the transparent shader.

I think this is a bug as I have encountered an obvious bug with objects instanced with the hair particle system.

If it’s not a bug, I would greatly appreciate some insight in how to avoid overlaying too much transparency with billboards.


The first render shows what happens if you replace the verticle billboard’s dead tree texture with a triangular solid that covers up the dead tree branches of the texture, perhaps limiting the complexity of the alpha map.

Thank you! Reps!