Hi, @hurricane86!
I changed the code. And no big progress here. Camera changes target angle to infinite(seems) distance - not on plane.
For test You can just place some plane object where projection matrix plane(portal/window) should be, and focus/orbit camera on it. That plane must stay still at any circumstances.
I’ll try to multiply camera rotation. So it points on my object on 0,0,0 relatively to projection.
And You told that previously I was already moving the camera, but I tried to not move it…it modified proj.matrix, but did not rotate view on point on projection plane…it moved view paralelly…again, as focusing point is in infinite distance, not on portal 0 point…how to control that?