   OpenGLES 2D Rounding Errors
  Hi,I'm attempting to convert a DirectDraw game into OpenGL, but am having trouble getting pixel-perfect 2D sprites to work.Since device coordinates are normalized, rounding occurs twice - once when multiplying with the projection matrix to get device coordinates, and again when transforming into window coordinates using the viewport equation. Even though my projection matrix sets up screen coordinates that match the window coordinates (i.e. 320x240), drawing a full-screen textured quad does not perfectly draw the intended image, with pixel errors distributed across the image, depending on how I choose the projection matrix.Note that this happens not only with 16.16 fixed point numbers in OpenGLES, but also with floating point numbers under regular OpenGL.Is there a way to avoid using normalized device coordinates in OpenGL? Any other suggestions for avoiding rounding errors? It would be unfortunate if imposing normalized device coordinates were to make OpenGL unusable for pixel-perfect 2D. Other than SDL, are there other free cross-platform embedded options available?Thanks!Zen   