Years ago I remember rendering some high-res animation frames for film by rendering each quadrant of the scene separately and combining the four pieces. Now I can’t remember how to do that. It’s basically fiddling with the window/viewport settings, isn’t it? I want to produce a frame that is twice (or 4x,8x etc) larger than the original, but otherwise the same. Any tips on the easiest way to do that?
Thanks!
Projection matrix.
With modern OpenGL (3.0+ or the ARB_framebuffer_object extension), you’d use a framebuffer object rather than rendering to the window. If you have enough video memory, you might be able to render it in one pass. Otherwise, using multiple framebuffers in a round-robin should be faster than using a single framebuffer, as you can read out the previous tile while rendering the next one.
Ok thanks – but how exactly do I need to change the projection matrix so that it produces a quarter of my original scene?
Put a scale and translation in front of it:
glTranslatef(nx-(2*x+1), ny-(2*y+1), 0);
glScalef(nx, ny, 1);
gluPerspective(...);
x and y are the tile indices, nx and ny are the number of tiles in each direction.