Here a screenshot of the differences, both methods are completely the same, but one renders to a pwindow and the other to a window. Both renderers have @depth_enable 1 (in the inspector)
The window output is correct: an image with another image in top with alpha blending. In the pwindow, you only seem to see the bottom of the 2 images (the one that is rendered first) and the second seems to be ignored.
Any ideas why? It seems to me this is all quite straightforward and there shouldn't be such a great distance.
Or is there a better way to do this overlaying thing to save to a disk? The bottom image should be rotated and moved and scaled according to runtime variables. I was planning on doing this by rotating the jit.gl.videoplane.