This subject actually appears in the FAQ at the McNeel site, but they overlooked the most important point: Regeneration.
AccuRender is a bit lacking in the area of curve "tessellation" but it’s not really AccuRender’s fault that the curves look square – it’s a little bit AutoCAD’s too. AutoCAD displays all curves with straight lines so that it can draw faster. How round your circles look depends on how close you were looking at them the last time you regenerated the drawing. Take a look – zoom right out and regenerate. Now zoom in on one of your circles – it’s a polygon. Regenerate again and watch how the circle turns round.
The trick is to zoom out to the right level and regenerate. Then load the model into AccuRender, and render that. There’s no real way of knowing where the right point is, you just have to guess. Be warned, though, that zooming in too close will cause the model to become too detailed, and may slow the rendering too much.
Some other controls change the resolution of curved objects. They are the system variables VIEWRES and FACETRES. They change the relationship between the zoom level and the number of straight lines your circles are converted into. McNeel recommends that you set VIEWRES to 100 and FACETRES to 0.5. Others suggest that FACETRES could be much higher – 10 even. Experiment and see. Everything still depends upon your last zoom and regen though.
One other control only works for thick polylines and other similar objects. In the AccuRender Object Properties dialog box you can tag an object for "curve tessellation." This lets you set the number of straight line segments in a circle directly. Beware though, if you are using very shallow curves you will need to set this number very high – perhaps as much as 300. Normally it is fine set around 15-20.
If you still can’t get your curves to translate properly after reading this, just cheat. Make your curved objects out of polygons with many sides – 20 is normally enough for a circle. This way you know exactly how they will look.
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