Just wanted to drop by to say thanks!
I have been using SDL for hobby projects for (I think) over 15 years. Programming little games is a great way for me to relax in the evening. SDL_RenderGeometry is a game changer for me. It made one of my projects run several times faster, using a fraction of the GPU/CPU.
However, I’m really happy you didn’t implement it any sooner. Over the last two years I (successfully) tried to understand how the basics of 3D graphics work. Starting by figuring out how to draw triangles by only drawing individual pixels and lines. I wouldn’t have had the patience to stick with it if that feature had been available. 
(looking forward to the 3D features!)
