Andrew_R provided the following information in our Archived Mailing List.

You can draw GL transitions and in various environments:

• In Vanilla WebGL code, gl-transition exposes a draw function to render a GL Transition frame.
• With regl, regl-transition exposes a function to render a GL Transition with a regl context.
• In React paradigm, react-gl-transition exposes a <GLTransition /> component to use in a gl-react's Surface. This is what this app uses heavily.
• In CLI, gl-transition-scripts exposes a gl-transition-render command to render a Transition to an image file. Our bot uses that to render a GIF and put it in the PRs! Travis also validates the transitions that gets committed with the gl-transition-transform command.
• In a node.js server you can use headless gl and obviously gl-transition to render a transition on server side. Which is what the gl-transition-render command is doing.
• ...more environments and languages to support are welcomed to contributions.

I think most Cinelerra users who read this forum use the "Video Transitions" included with the CinGG AppImage that is built in (and so may not have looked at gl-transitions.com).  I brought up its website and it looks very good but I did not load or test the actual software.  It does seem to be quite robust and useful.

Cinelerra built in Video and a few Audio Transitions work well and do use the Graphics Library (GL) when enabled and able to do so.  There is a demo of the available Video Transitions currently available and others can be added by the user.  Demo is at:

   https://streamable.com/7qb7l0

There are currently about 70 Video Transitions built in and are listed at:

   https://cinelerra-gg.org/download/CinelerraGG_Manual/Shape_Wipe.html

An older created video is a nice display of the transitions and can be downloaded as described in:

   https://cinelerra-gg.org/forum/look-at-me-link-to-results/show-off-cinelerra-transition-with-flowers/

Web site: https://gl-transitions.com/

Thanks in advance!!

Steve_Bass