SeparateAlphaBlendEnable flag in Unity?

Unity Engine
1

Hello,

I’m trying to implement the Off screen particle system described in GPU Gems 3, and found that it need some special render flag for alpha channel blending, it states that it’s a DX9 feature but I couldn’t find it in the Unity doc, any ideas? Thanks

2

You can’t set it at all I fear. You have no access to render flags, the only flags you can set are blend flags.

Question is what it is used for and if the same effect can be achieved differently basing on unitys render pipeline

3

It’s used for alpha channel blending which requires a different blending mode versus RGB channels, in the GPU Gems3 article it was used for particle composition. I can achieve the same effect in Unity, however it requires an additional render pass for particles which is not a performance wise solution.

4

Question was less about what it does but what it is used for in detail, not sure I got it from this explanation.

There are a few things that can be set for shaders?

  1. Set the renderqueue to alpha?
  2. Use the render mask to specify it to be A instead of default which is ARGB?
  3. Distinct camera rendering to render texture with exactly what you want it to contain to overlay?
  4. Replacement shaders?

Generally offscreen is such a topic in Unity you might not end happy, as you have no control over culling, especially if it leaves the frustum. You might need to use a camera in some way, be it a camera with a depth higher than your normal one so its rendered “behind it and never seen” or whatever

5

http://technology.blurst.com/off-screen-particle-optimization/