I need to render to a viewport that is slightly off the screen. For example, instead of the viewport's top left coordinate being at 0,0 I would like it to be at -10,-10.
The problem is that all the video drivers have a setViewPort() function that clips to fixed dimensions (defined as the top left being at 0,0 and the bottom right set from the current getCurrentRenderTargetSize()).
Because this clipping results in my output dimensions changing (ie my output width and/or height are altered), this means that the projection is changed. Obviously, this results in rendering looking incorrect because it appears squashed.
I suspect that the reason for the clip is that OpenGL/DirectX cannot handle a viewport offscreen? Is that the case?
If so, does anyone have any idea as to how I can get around this limitation?
well you can render the scene to a texture and then render a screen quad slitly setoff with the texture applied that will work for sure.
We're programmers. Programmers are, in their hearts, architects, and the first thing they want to do when they get to a site is to bulldoze the place flat and build something grand. We're not excited by renovation:tinkering,improving,planting flower beds.
We're programmers. Programmers are, in their hearts, architects, and the first thing they want to do when they get to a site is to bulldoze the place flat and build something grand. We're not excited by renovation:tinkering,improving,planting flower beds.
Rending to texture and then rendering that texture to a quad has a negligible performance increase over rendering directly to the screen buffer. That's why post-processing is done this way.
I challenge you to try this before stating that it will be too slow.
Do two programs. Make a rotating cube. Stick a camera in front of it. In one program, render straight to screen. In the other program, render to an RTT and use a quad to render to screen.
As far as I'm aware, there's no way to have an offscreen viewport. Render to texture and then render that texture to a fullscreen quad, using UV coordinates to offset your image. For example, if you wanted the upper left corner to be 10% inside the image, you'd make the UV coordinate (0.1, 0.1).
