tapered versus standard extrude

[W Wilkerson]

I am trying to indicate a floor with a 6" wide border of the same thickness. I intially drew the border, say a 10'x10' square, added an additional 6" border around it, and did a 0? tapered extrude of 1/4" so that I would have quick Z-Axis control. I then did a hidden line rendering, and some of the detail, the interior perimeter of the 6" border disappeared. I redid the object as a standard extrude, and everything showed up upon doing a hidden line rendering.

I teach a class on VW, and it would be useful to explain to students why this occurs. Any ideas? One of my peer users suggested some rounding errors in the vectormath, but that is beyond my realm of expertise.

Thanks, weston

[islandmon]

It seems to me that you're describing two different geometries :

1) Standard Extruded floor

2) Tapered Extruded 6" perimeter baseboard

The difference between the two defines the problem. The Floor requires 6 3dPolygons, whereas the tapered baseboard requires 12 3dPolygons to describe it.

However, using TaperedExtrude only produces the 6 exterior faces.

Therefore, to achieve a tapered extrude with 12 faces you will need to ExtrudeAlongPath or RevolveWithRail.