Forums - Vulkan, Pointsprites performance and Alpha Blending

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Vulkan, Pointsprites performance and Alpha Blending
GilesGoat
Join Date: 15 Jul 14
Posts: 5
Posted: Thu, 2020-06-04 12:09
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Hi,

I have two related questions here, as I am working on a software for Oculus Quest, Vulkan based, where for a particular effect we are drawing with a single draw call a number of PointSprites ( approx 32,000 ) with some alpha blending active  ( and NO Z-buffer used ).

We are finding out that "as long as gl_PointSize is <= 48" performance is pretty high but if poinsprite gets "a bit too big or too close to the user" perfomance drop and "quite a lot of it" seems cause the fact Alpha Blending is active.

So two questions here ( related ) :

- is it efficent to draw points with gl_PointSize >1 ( i.e. is the "pointsprite generation efficient ?" ) or let's say maybe drawing a single quad with instancing could be better ? ( i.e. use a buffer containing a single quad, draw in screen space, use it as base for an instanced drawing ? )

- is alpha blending "heavy" on the Adreno ? Are there any suggestions do/don'ts when using Alpha to get better performance ?

Thanks in advance.

 

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