I have a function that renders a simple OpenGL scene. I want to display this scene on a polygon within another scene, without the function having to know about it. For example, to display the scene on the red polygon indicated:
I can set up the projection and modelview matrices to render to a small rectangle on the screen, but that doesn't work in a case like the image shown, where the target polygon is transformed and is no longer a rectangle on the screen. Is it possible to render to a non-rectangular target like this? The target is defined by four vertices, and I'm just not sure how to put those into the matrices.
I am aware of VBO/FBO functions that can render the sub-scene to a texture, which could then be mapped onto the polygon. However, this would be a bit more work as I'd have to add support for these functions to LuaGL, and I get the feeling it'd be slower than simply altering the display matrices - if it can even be done that way.