Comments on: iPhone 2D projection matrix, FPU

By: Abe Pralle

Abe Pralle — Sat, 21 Nov 2009 20:34:13 +0000

I rolled my own – made an array that contained all the matrix values and then wrote custom matrix multiplication routines; I do all the transforms myself before sending vertices to OpenGL.

However, after this post I figured out a solution that got rid of the imprecision in glOrthof: using the fixed-precision orthox methods got rid of the error – so, for example:

glOrthox( 0, 320<<16, 480<<16, 0, -1<<16, 1<<16 );

By: Miguel

Miguel — Sat, 21 Nov 2009 08:23:41 +0000

Hey abe, this may be a noob question, but how were u able to impose your 3X3 matrix as the projection matrix? the only functions i see are translate, rotate, and scale. I can create a M3dMatrix, but then how would I impose it as the projection? without calling glOrthof(float, float, float, float).

By: Richard Harrison

Richard Harrison — Sat, 16 May 2009 04:57:01 +0000

I haven’t got my Iphone dev environment yet but from Intel experience I would query whether the slowdown might come from memory access and register loading. I would be interested to see the comparison with adding two 256 x 256 arrays together.

By: joeedh

joeedh — Tue, 14 Apr 2009 16:24:11 +0000

awesome! makes me want to get a mac to play with iphone development

By: Jacob Stevens

Jacob Stevens — Fri, 10 Apr 2009 19:13:35 +0000

Awesome! We use a lot of doubles so I’m relieved there’s no major performance hit.

Great work!

Jacob