I know the PyOpenGL mailing list might be a better place to ask this
question, but I've had a lot of luck talking to the experienced
people here so I figured I'd try it first.
I'm trying to migrate a game I created from using the Pygame / SDL
software rendering to OpenGL. Before attempting the massive and
complex conversion involved with moving the whole game, I decided to
make a little test program while I learned OpenGL.
In this test, I set up OpenGL to work in 2D and began loading images
into texture objects and drawing textured quads as sprites. I
created a little glSprite class to handle the drawing and
translation. At first its draw routine looked like this:
glPushMatrix()
glTranslate(self.positionx,self.positiony,0)
glBindTexture(GL_TEXTURE_2D, self.texture)
glBegin(GL_QUADS)
glTexCoord2f(0, 1)
glVertex2f(0, 0)
glTexCoord2f(1, 1)
glVertex2f(w, 0)
glTexCoord2f(1, 0)
glVertex2f(w, h)
glTexCoord2f(0, 0)
glVertex2f(0, h)
glEnd()
glPopMatrix()
Note: self.texture is a texture ID of a loaded OpenGL texture
object. My sprite class keeps a dictionary cache and only loads the
sprite's image into a texture if it needs to.
I'd get maybe 200 identical sprites (same texture) onscreen and my
CPU would hit 100% load from Python execution. I looked into what
could be causing this and found out that it's probably function call
overhead. That's 14 external library function calls per sprite draw.
The next thing I tried was to create a display list at each sprite's
initialization. Then my code looked like this:
glPushMatrix()
glTranslate(self.positionx,self.positiony,0)
glCallList(self.displist)
glPopMatrix()
Well, that's nice, down to 4 calls per draw. I was able to push ~500
sprites per frame using this method before the CPU tapped out. I
need more speed than this. My game logic uses 30-40% of the CPU
alone and I'd like to push at least 1000 sprites. What can I do?
I've looked into passing sprites as a matrix with vertex arrays, but
forming a proper vertex array with numpy can sometimes be more
trouble than it's worth. Plus, I can't swap out textures easily mid-
draw, so it makes things much more complex than the simple way I'm
doing things now.
Is there any design pattern I could follow that will get me more
speed without sending me off the deep end with complexity.
Thanks,
Zack