I want to render pictures with resolution bigger than the screen resolution and save the pictures to bmp file. I tried to use window width and height bigger than the current visible window, render the scene in the default draw buffer, read the buffer, and save to file. But when I looked at the bmp file, it had only the lower left corner of the picture and other area were all gray. The lower left part seemed correctly rendered (color, scale, etc.) and the size of that part was exactly same as the visible window size when I did the rendering and saving.
Is that because the frame buffer is of the same size as the visible window? How can I use a frame buffer that is larger? Does windows support aux buffers? How do I specify the buffer size?
Hope to get help. Thanks,