6 BGE Alpha Blend types explained

This was always confusing to me and the information is hard to get anywhere apart from experience and tool-tips.

Hopefully you guys will find this useful :D!

Nice guide. Very clear!
Thanks Thatimster.

Nice tutorial.

As far as I know the difference between alpha blend and alpha sort is that alpha blend calculates the z buffer value (which to draw on top) based on the object position, while alpha sort calculates it for each poly. This means that while very processor intensive, alpha sort could be good for things like a character’s hair, which are usually one single object with lots of planes, rather than many different objects.
A side effect of this is that if you are using alpha blend, but the object’s center doesn’t match the center of geometry you’ll get strange results with the plane being rendered behind things it should be in front of and vice versa.

Add alpha is very processor efficient. It’s very good for doing effects like fire, since the z depth doesn’t matter. Whether it is rendered in front or behind is irrelevant since the result of 1 + 2 is the same as 2 +1.

To add…
Non-planar poly (quad n above) may cause alpha sorting problem.
The best option for curved alpha-sorted object is by using tris.

Right, this makes more sense! Information like this is hard to find in the docs.
So the proper order would be:

  1. Alpha anti-aliasing
  2. Alpha clip
  3. Alpha add
  4. Opaque/Blend
  5. Alpha sort

This ties in well with what smoking_mirror was saying about each poly being calculated, as if you don’t have lots of tris then this is hard to calculate for the engine.