Pixel-Perfect 2D Rendering with OpenGL

Question

Is it possible to set up an OpenGL scene to allow for pixel-perfect rendering and pixel blitting? I noticed that setting up a scene by doing:

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, width, height, 0.0, 0.0, 1.0);

And then drawing a pixel using:

glBegin(GL_POINTS);
glVertex2i(0, 0);
glEnd();

Does not consistently draw it on the top-left pixel on every hardware configuration (sometimes it's one pixel to the left, or one below the top-left corner). I realize this is likely due to different implementations of OpenGL by the graphics drivers, but is there a way to make it so that the top-left pixel is (0,0) and the bottom right is (width-1, height-1) consistently? It seems strange that this is something that isn't standardized...

I've seen some 'hacks' that use a translation of (0.375, 0.375) or (0.5, 0.5), but that also seems to solve it for some configurations and not for others.

Answer 1

edit: dang, it is a translation. Updated.

You've got to consider also that pixels have size too. This is what the "translation hacks" are getting at. If the leftmost pixel should have a center coordinate 0.0, then its left boundary is at -0.5 -- and that's where the clipping plane should be. Similarly, if the rightmost pixel should have a center coordinate width - 1, then its right boundary is at (width - 1) + 0.5 -- and that's where that clipping plane should be.

So try:

glOrtho(-0.5, (width - 1) + 0.5, (height - 1) + 0.5, -0.5, 0.0, 1.0);

So that's where the translation come from.