My original target was iOS, so this was unavailable. I did experiment with their algorithm, but 4x MSAA was slow and had poor quality compared to Core Graphics, which was my reference.
Drawing cached renders in quads is how Core Animation works, but they do not scale well. You are ultimately limited by the CPU. Rasterizer enables a fully-animated canvas @ 60fps.
The longer answer is that using straight-edged geometry to represent curves is a resolution-dependent operation, e.g. a full screen circle may need to be flattened to an 80-sided polygon.
Rasterizer can solve quadratic curves in the fragment shaders, which massively reduces the geometry needed for a scene.
Also, the native rasterizer only supports MSAA, which is inferior to reference analytic area AA.
Rasterizer excels at animation and complex scenes, e.g. 2D CAD documents. The original inspiration was Flash, as I love innovative design tools. Flash 1.0 could easily be used by designers, but ultimately lost its way became a coder's toy after the Adobe acquisition and ActionScript 2.0.
Fleshing out the spec is planned, but I cannot provide a timeline as this has all been done at my own considerable expense. Maybe if my tips grow: https://paypal.me/mindbrix
The "traditional graphics pipeline" approach was chosen to maximise the platforms Rasterizer could run on, as GPU compute support at the time was patchy. Compute is now more universal, so Rasterizer could move that way.
SDFs are expensive to calculate, and have too many limitations to be practical for a general-purpose vector engine.
Vello is general purpose, like Rasterizer, but is based on GPU compute. Rasterizer uses the 'traditional' GPU pipeline. Performance numbers for both look very competitive, although Vello seems to have issues with GPU lock up at certain zoom scales. Rasterizer has been heavily tested with huge scenes at any scale.