Render registration result

Hi, all.

This question is related to

Rendering for CT and dsa registration - Development - 3D Slicer Community

My partner want to display projected plane . and take 3d view as renderwindow

the reques is as below:

1- mouse event , such as scale is invalid.

The projected contour only changed if moved or rotate.

2 - the contour or renderwindow should be transparent, so DSA image in background can be displayed

Is it possible to do this?

Or is it easier to render image in slice/2d window, Then I think should add custom mouse event in 2d window

Any suggestion will be very appreciated!