Thanks Dave. The primitives can be fun to work with, if time consuming.
And yeah, poser 4 and 5 render a bit differently.
In 4, as you know, the rendering process does a sort of 'pass' over the screen. A line sweeps from bottom to top (or top to bottom), and samples every pixel that it passes over.
In 5, the renderer uses what it calls 'buckets'. A bucket is a square on the screen that covers a small area (the default is 32x32 pixels but you can change it). The square moves from left to right over the screen. When it reaches the end of a line, it goes back to the left and to the next line under it, like a typewriter. The render continues in this way until the entire screen has been sampled. Those weird lines appear at the edges of where the render bucket appears, usually only if very high quality settings are used. A bit of a conundrum.
This may only happen on my computer, but it has caused me to use the p4 render (which is an option available in p5) on more than one occasion.