The smoothness (tesselation) of curved curtain wall edges is controlled by the FACETDEV variable. Specify the facet deviation to set the number of facets to display on curved objects. This must be set before converting a polyline to a curtain wall.
The facet deviation is available only on the command line by typing aecfacetdev.
The number you set as the facet deviation defines the maximum distance from the chord to the arc, the chord being an edge that is created from faceting the curve, to the true mathematical arc. The facet deviation has a range of greater than zero (0) and no upper limit.
The minimum number of facets is 8. For example, when you create a cylinder mass element with a 1' radius, and specify a FACETDEV value of 1', the cylinder has 8 faces.