Render using "real" raytracing was much slower than using sort of scanline rendering without real raytracing, as 3D studio and I think also Lightwave did. How many times you want to calculate reflecting light beams has of course extreme impact on rendering time. Glass is the most time consuming when using raytracing.
I also think that Lightwave used a processor on the Video Toaster in addition when rendering. It was possible to render in network, using many Amiga's.
The Amiga Juggler demo released in 1986 was rendered on a 512 Kb Amiga 1000 (7,14 MHz 68K). Each frame took about or maybe less than one hour to render, not to bad, real raytracing, but maybe a little simpler than glass in Real 3D.