png_write_rows and performance

[squisher]

Noticed I was getting some graphical frame rate lag with just 50 objects on the screen, and profiled my client with Very Sleepy. Following are the results:

Code: Select all

Name                    Exclusive, Inclusive,%Exclusive,%Inclusive, Module 
png_write_rows,         11.245545, 28.617578, 32.021381, 81.487769, Irrlicht
SetEvent,                1.724862,  1.724862,  4.911497,  4.911497, KERNELBASE
SetThreadAffinityMask,   1.501838,  1.501838,  4.276443,  4.276443, kernel32
RtlAllocateHeap,         1.461976,  1.463975,  4.162937,  4.168629, ntdll
HeapFree,                1.443923,  1.449921,  4.111531,  4.128610, kernel32
GetProcessAffinityMask,  1.194603,  1.201616,  3.401599,  3.421569, kernel32
RtlEnterCriticalSection, 0.546095,  0.546095,  1.554991,  1.554991, ntdll

As you can see, the overwhelming majority of render time is spent in png_write_rows. I use png format for all my textures and gui elements. The only special materials I'm using are sphere maps. Am I making a blunder by using the png format? Should I be using a different format instead? (I do need an alpha channel). Or would the problem have to lie elsewhere, such as too many image files or too big image files?

[CuteAlien]

Why do you have png-writing while rendering stuff. Recording screenshots?

[squisher]

nope

[CuteAlien]

Strange, I don't really see why this function would be used in rendering. Can you set a breakpoint in it and see where it's called from?