I have to disagree with some of the verdicts on Strata3d. This is vastly superior to previous versions - but it does require a recent-ish machine running OS 8.6 or higher.
I would put programs mentioned in the following order, once power and intuitiveness are taken into account.
1 Strata3d
2 Amapi (intuitive and powerful, but limited rendering)
3 Bryce (good rendering, intuitive, but poor modelling)
4 Pixels 3d (very powerful modeller, but a tad buggy and limited rendering)
5 Stratavision 5
6 Stratavision 4
7 Mechanisto (less intuitive and not particularly powerful)
8 POV Ray (v unintuitive)
9 RenderBoy (v unintuitive)
10 3dJoy (not much to recommend it)
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M A R T I N Β T U R N E R