Issues rendering two scenes at the same time

[patrikant]

I am trying to render two scenes of the same object but with different resolutions. To switch between the two scenes, I use a slider with gl.scissor.

I am facing some issues with this. Using one renderer on one canvas shows nothing without any errors when the renderer is called twice in the requestAnimationFrame with different scenes. Using two renderers on one canvas shows the correct cutted result for each scene IF only one is rendered at each time. If the second is rendered as well, the second is shown correct, but it biases the other scene. Even with gl.scissor

Any idea what could cause these issues?