[Bf-python] Blender-python API/functionality proposals

[Dima Glibitsky]

> Depth buffer and color buffer are possible to get with bgl (the opengl
> wrapper).

Yes... But I'm also interested in the intermediate buffers' values --
for example, if any visible object has X-Ray turned on, the final
ZBuffer would contain values only for X-Ray objects.

Hmm, perhaps Blender does not actually store the intermediate
buffers... So, I guess, this part of proposal should be reformulated:

3) Introduce python callbacks that would be invoked after the
corresponding stages of the viewport rendering. E.g.:
bpy.app.handlers.view3d_pass_zbuffer
bpy.app.handlers.view3d_pass_zbuffer_xray
bpy.app.handlers.view3d_pass_selection_buffer
etc. (I don't know what render passes Blender actually does, so these
are just an imaginary example).
The corresponding callbacks might have a signature like
callback(context), where context contains information about the
corresponding area/space/region.

Also, to get correct values via glReadPixels(), you need to know the
absolute coordinates of the region you're working with. Blender does
not seem to provide that information (at least I couldn't find it in
the description of the corresponding classes), only the region's width
and height.