DOOM and Wolfenstein weren’t conventional 3D. They used ray casting, which is essentially mode 7 - taking slices of 2D and compiling them together to create a seemingly 3D image.
But even before that, full polygons were being rendered in monochromatic vector systems. And I’m sure you could probably find research being done on this stuff before people were able to practically apply them to whatever computer systems existed at the time.
I think you’d be hard pressed to find any one person responsible for the having invented the 3D engine.
