Can anything make Graphics Analyzer to report wrong overdraws? I ask because my scene has one draw call of a rather simple geometry causing the overdraw to jump from 0 to 8 on the output pixels. Back face culling is on. I can't think of anything else that would make it have such a huge jump. Is there any GL state that I should be wary about? I am hovering the mouse pointer over the output pixels and the histogram also show a large amount of 8x overdraw pixels.
Hi Denis, Nothing immediately jumps to mind. Are you able to share the captured data file? Feel free to get in touch at developer <at> arm <dot> com if you can't share this publicly.
Thanks Peter, I've sent an email to developer <at> arm <dot> com.
Hi Peter, I think now I understand what is going on. The problem is that overdraw analysis is, for some unknown reason to me, not shading as grayscale. Sometimes it partially shade things in grayscale, and sometimes the whole scene is just with normal colourful shading. Graphics Analyzer is probably using the pixel colour to analyse the overdraw and hence the parts that fail to be shaded as grayscale returns the wrong overdraw count. The histogram is therefore affected as well. So the question is now why am I not seeing the whole frame as grayscale, and why sometimes it completely ignores the fact I am doing an overdraw analysis and just shade it with normal colours?
We implement overdraw using shader replacement, so it sounds like our shader replacement for overdraw is failing on one of your render passes. Your email never seemed to arrive our side - if you need more help can you try and send it again?
Hi Peter, I have resent the email with the same subject as this thread.
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