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Why is this so slow?

DanG · 2002-08-30T20:08:12

I was working &#111n getting some image handling code working when I realized that the framerates I was getting, doing almost nothing, were terrible. All I do each frame is draw 2 256x256 bitmaps at 2 spots &#111n the screen, here is the code: glRasterPos2f(-.5,-.5); glDrawPixels(m_Image.Width(), m_Image.Height(), m_Image.Format (), GL_UNSIGNED_BYTE, m_Image.Data()); glRasterPos2f(0, 0); glDrawPixels(m_Image2.Width(), m_Image2.Height(), m_Image2.Format(), GL_UNSIGNED_BYTE, m_Image2.Data()); I''m &#111nly getting 7-8 FPS. Awful! My profiling (done with a code profiler from Game Gems) shows that 70% of the time is spent &#111n that code. My computer isn''t to0 great (500 mhz, ATI Rage Pro 2mb) but it can do A HECK OF A LOT MORE than draw to images in 120 ms. What could I be doing to make this so slow?

General and Gameplay Programming Programming

Started by DanG August 30, 2002 01:07 PM

10 comments, last by DanG 21 years, 7 months ago

Z01

134

August 30, 2002 08:04 PM

A bit more explaination of previous posts...

The card is capable of pushing a lot more polygons than you are seeing, but if the card doesn''t support OpenGL, the OpenGL implementation probably reverts to a software renderer. (I am not 100% sure if OpenGL does this... I know DirectX reverts to the Hardware Emulation Layer when a feature is not supported in the card.)

And a software renderer is sloooooowww.... I have a 1.2Ghz Athlon and Geforce2 and I usually see a frame rate drop anywhere from 5 to 200 times when I''m running using a software renderer, depending what I''m doing. Software renderers also depend on your CPU speed and your CPU is slow. Thats my guess about what is happening.

Btw, if your card has crappy support for OpenGL, it probably has reasonably good DX support. A lot of the old old cards supported either DX or OpenGL, and a few supported both. The new cards all support both APIs.