## Re: [PyOpenGL-Users] 2d sprite engine performance.

 Re: [PyOpenGL-Users] 2d sprite engine performance. From: Mike C. Fletcher - 2005-04-07 00:41:08 ```Erik Johnson wrote: ... >>so a sprite's >>move command would look like: >> >> self.getSpriteVectors()[self.startIndex:self.stopIndex] += delta >> >>(where delta would be a simple tuple), allowing the array to handle >>updates in Numpy code. >> >> > >I might need to learn more about Numeric. I didn't know that you could >do things like the above and have Numeric take care of it without Python >doing a bunch of intermediate steps behind the scene. > > They are fairly serious about allowing efficient number crunching :) . We just go along for the ride on the backs of their work :) . Particularly, the in-place modifiers are a big part of the Numpy interface. By the way, watch out for them too: In [6]:a = arange( 20 ) In [7]:b = a[5:8] In [8]:b += 5 In [9]:a Out[9]: array([ 0, 1, 2, 3, 4, 10, 11, 12, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]) that's the same feature that allows the += delta, but it can bite you if you don't keep in mind that the sliced array is pointing to the same memory area as the original array. >I thought that contiguous() just checked if the array in question could >be passed to opengl directly as a pointer instead of being copied. Am I >missing something? > > It does the check, and if the array *isn't* contiguous, it copies it into a contiguous array and returns that. The effect is accomplished with a fast Numpy flag-check, so if the array is contiguous (the normal case), then there's little performance impact. OpenGLContext, for instance, has a flag (default on) that just runs contiguous on every array it's going to pass to PyOpenGL for IndexedFaceSets. Have fun, Mike ________________________________________________ Mike C. Fletcher Designer, VR Plumber, Coder http://www.vrplumber.com http://blog.vrplumber.com ```