ExtractSrf not able to select through front surfaces

I use ExtractSrf to pick surfaces out of polysurfaces so they can be assigned to different layers. Think of a table top with laminate and and edge moulding. I want to extract the top and bottom surfaces from the polysurface. I can pick the surface that’s visible, but not the one behind it. This used to work in Rhino4, but now I have to rotate the view around to pick the 2nd surface.

It’s not a big deal, but it’s slower. Instead of clicking the poly twice to get the front and back face, I have to click-rotate-click. Is it supposed to work this way now?

Using Version 5 SR6 32-bit
(5.6.31009.7465, 10/9/2013)

I can repeat your problem only under the following circumstances:

  1. The object is an extrusion object
  2. The object has surface isocurves turned OFF

If i turn isocurves ON under Properties / Isocurve Density, it is possible to select the occluded surface once the surface in front has been picked. (If the object is an extrusion). For polysurfaces, i´m able to click the occluded surface even when isocurves are OFF. Tested in Shaded and Ghosted display mode.



I’m seeing the same thing here. Polysurfaces seem to work correctly, extrusions don’t.

I also noticed something weird testing this with simple boxes: A box made with the box command is an extrusion object. A box made with bounding box is a polysurface… Why would anything that wasn’t extruded be an extrusion?


Hi JT- lightweight extrusions can be used to represent objects that are linear in one direction at least and have planar curves defining the profile- that is, if they could be extruded from planar curves or faces, they tend to be made as extrusions. BoundingBox could also use extrusions, it just never got done, I guess.