When you try to export a video with the --transparent flag and the opengl renderer, the output video doesn't have any alpha channel.
Expected behavior
Rendered video should have transparency (alpha channel).
How to reproduce the issue
Use a ThreeDScene or Scene (the problem is the renderer, not the scene) with some OpenGLRectangle (or OpenGLMobject you want), set the self.camera.background_opacity = 0 and use the --renderer opengl and the -t tags/flags.
Additional comments
If you check the opengl_renderer.py file, that is the specific renderer that takes part when you send that flag, you can see in the line 596 that the background color is forced to have 1.0 as alpha background. This means that the background will never be transparent. That alpha value should check if the flag --transparent is set as True, as the cairo_renderer.py does, or at least allow you changing that value.
Even in the update_frame method of that file, if you manually force the background_color to be (0, 0, 0, 0) as a numpy array, it is set as 1.0 for the alpha as the setter is forcing it.
Description of bug / unexpected behavior
When you try to export a video with the
--transparentflag and theopenglrenderer, the output video doesn't have any alpha channel.Expected behavior
Rendered video should have transparency (alpha channel).
How to reproduce the issue
Use a
ThreeDSceneorScene(the problem is the renderer, not the scene) with someOpenGLRectangle(orOpenGLMobjectyou want), set theself.camera.background_opacity = 0and use the--renderer opengland the-ttags/flags.Additional comments
If you check the
opengl_renderer.pyfile, that is the specific renderer that takes part when you send that flag, you can see in the line 596 that the background color is forced to have1.0as alpha background. This means that the background will never be transparent. That alpha value should check if the flag--transparentis set asTrue, as thecairo_renderer.pydoes, or at least allow you changing that value.Even in the
update_framemethod of that file, if you manually force thebackground_colorto be (0, 0, 0, 0) as a numpy array, it is set as1.0for the alpha as the setter is forcing it.