Cause of Alpha or Black Artefacts in Render This is my Minecraft Animation. It is made in Blender Internal and is intended to be rendered in Blender Internal. The animation consists of me running infront of Minecraft trees. These trees are mapped with UV textures of Minecraft Leaves with alpha turned on so that the leaves are transparent in places. The Animation starts at frame 8 and ends at 40. This is not a case Z fighting.

However when I render the animation I get square alpha (sometimes black pixel) artefacts in the render. Every frame has diffrent result but still has the artefacts. This is what it looks like. The white is the alpha. Open in a new tab for closer inspection.



As I said some frames have this problem and some don't



This one has AA disabled. This makes the alpha only one pixel each. (Open in new tab to see individual pixels)


This problem does not occur in the rendered mode viewport.


Leaves' Material Settings




Leaves' Texture Settings




Edit: I decided to restrict the leaves from render and this is the result I have. Pretty ugly. Also added, glare and vector nodes just fyi.



I then decided to remove the wood as well and now this happened.



And now there's black and alpha.



Here is a link to a video showing the problem.

What is going on here! Is this blend file corrupted? Please if you know the answer or what causes this please mention this down below.

And because you asked here a stripped down version of the file: https://www.dropbox.com/s/4q5qfsmjv7umtbh/Stripped%20Down.blend?dl=0
The artifacts are not from z-fighting, but from transparent auto shadows bias.

Just turn the option off:


Shadow auto bias on:


Shadow auto bias off:






Elaboration:

There was once bug which was (supposedly) fixed for 2.68:


  Found the cause of the problem, it's due to the ray bias options that tries to avoid bad ray traced shadows.


It's supposed to eliminate shadow artifacts on smooth shaded surfaces where the shadow terminator is - like this one (I think..):



My guess is that blender sometimes fails to get it automatically right, setting it to fix value then works better.

Or making the surface flat shaded should work also.