Imagination PowerVR SDK Blog

OpenGL ES 3.0 integer precision


#1

Hi, I’m working on a device with a PowerVR Rogue Hood (driver 1.3@2876724)
I’m surprised to see that a 2k14 device has only 24bit integer (high) precision (using glGetShaderPrecisionFormat), I thought it would be 32 nowadays …
(which may be the reason of some bugs I got on this device for a code running well on all other devices)

I understand that on this kind of device, only 24bit are valid in (u)integer.
Let’s consider the case of a TransformFeedback only (no rasterizer) vertex shader, outputing some uvec4 values in a 4xu32 buffer.
Will the shader compiler be smart enough to merge 16/24bit intermediate results to write valid 32bit results
or do I have to consider that at most 24 of the 32bit of the output will be valid ?
(and in this case, will the top 8bit be cleared, set or undefined ?)


#2

Hi,



We’ve looked at the driver source and confirmed this is a bug. The 1.3 driver you’re using incorrectly reports 24-bits instead of 32-bits.



As of changelist 3206984, all glGetShaderPrecisionFormat() values were corrected.


(which may be the reason of some bugs I got on this device for a code running well on all other devices)

If you can create a new discussion chain for the bugs you've encountered, we can help you investigate. If you need to share any builds or logs with us confidentially, you can attach them to tickets in our support system: https://pvrsupport.imgtec.com/new-ticket

Joe