Iris Graphics Geometry Engines weren't programmable in the modern sense. There was a fixed pipeline of Matrix units, clippers and so on that fed the fixed function Raster Engines. You could change various state that went into the various stages, but the pipeline's operations were fixed.
Later SGI Geometry Engines used custom, very specialized DSP-like processors, but the microcode for those were written by SGI, and not end-user programmable.
There were probably research systems before it, but AFAIK the Geforce 3 was the first (highly limited) programmable geometry processor that was generally commercially available.
Later SGI Geometry Engines used custom, very specialized DSP-like processors, but the microcode for those were written by SGI, and not end-user programmable.
There were probably research systems before it, but AFAIK the Geforce 3 was the first (highly limited) programmable geometry processor that was generally commercially available.