ACA: Curved Mass Elements – Part 1: FacetDev and FacetMax

A thread in the AutoCAD® Architecture Forum last month brought to my attention that I have not yet addressed how AutoCAD Architecture handles “curved” Mass Elements. “Curved” is in quotation marks because AutoCAD Architecture does not display Mass Elements with true curves, but instead will approximate curves with a series of straight-line segments (2D) or facets (3D).

In the image above, a Mass Element Cylinder with a radius of 10′-0″ and a height of 5′-0″ has been placed, with FacetDev set to 10′-0″ to make the facets obvious.

Two settings control the number of segments that are generated, FacetDev and FacetMax:

  • FacetDev is the allowable deviation of a facet from the true curve, and represents the maximum distance allowed from the midpoint of a facet, perpendicular to the true curve. Larger values will generate fewer facets. Smaller values will generate more facets. A full circle will never have less than eight segments, as seen in the image above. FacetDev must be a…

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