Nontransparent patches rendered transparent in Cycles? Original .blend file: https://www.dropbox.com/s/dlipv36yu28rk46/SE.blend?dl=0 (~120MB)



I manually segment out human body parts from an image and make each body part a .png image where the alpha channel is 1 for that body part and 0 anywhere else. So for example, I have a RGBA "leg image" as follows.



Now I use them as textures of planes that are stacked up at different heights in Blender, like this.



Here are the material node settings.



I then render them with Cycles under "full global illumination." Here is what I get.



Sorry for the typo -- should be right arm/leg

As you can see some body parts (e.g., right arm) look transparent, and some even completely disappear. Why does this happen, and how can I fix it?
Your planes are touching, Cycles can't figure out which is in front of what.

You have overlapping planes with or coinciding geometry in your scene.

Organize your blend file, be thorough move them apart in Z direction a consistent amount of units.