I have not set a background as I want it to be transparent. I save via OpenGL frames and save as PNG, but the background is black.
How can I solve this?
Try png4?
I think you are going to have to do it with a real render if you need that alpha information. The openGl doesn’t seem to allow it eventhough you have the “4” format like png4, tga4 or psd4.
What do you mean by “a real render”?
The OpenGL export is meant as a quick export but not of the best quality. If you didn’t set OpenGL to do full-scene anti-aliasing or on Windows you didn’t set the graphic card to do anti-aliasing your lines will be jaged in the final images.
Also it will not take into account effects you did in the Network view.
It follows the Display that you choose also instead of the Write module(s) in the Network.
Generally you should use Export>Render network and set the Write module to the file format or properties you want for the final output.
In Harmony database you can even use batch rendering options for bigger projects.