In few words…
I need to render a scene of 1920x1080 pixels for some background purposes. At the same time i need a smaller view of this scene with a size of 480x270.
If I create a context using my preview window of 480x270 then I only generate that number of rendered pixels.
I need to have a context rendering 1920x1080 pixels and I need a smaller resized preview of this with a size of 480x270 pixels.
In directx this came for free when creating a device with a large window and then simply shrinking it down but it seems that I need something extra in opengl.
How do I create one context and two views of its pixels?
The above was perhaps a little vague.
As I understand it, I need a render context for each of my “windows”. If I wanted two different views of the same scene, I could make a context current, render and do the same for the other context, but I do not want to render again. Instead I want to show the same rendered pixels in two different places.
I assume I could render the large version, copy it to a PBO using glreadpixels, change to small context and use glWritePixels, but… where will the resizing take place then? The pixel count is not the same.