This is one detail I never noticed before until I needed to export the Rhino model to SketchUp.
During modeling in Rhino 8 Ghostview, Sometimes the isocurve shows up, and sometimes not. It seems when the isocurve shows up, it is not considered a planar surface anymore. I used SelPlanarSrf to make a selection, all the surfaces with isocurve got skipped.
Found two ways to fix this:
By simply moving the edge within the same plane.
DupBoarder then PlanarSrf
Then I tried to understand why. I went to Grasshopper to check the flatness and curvatures of these surfaces. Here are the results:
The flatness component thinks they are all flat.
For some surfaces, the curvatures show (at a given point on its uv) jumping between 0 and -0.
Some of the surfaces with a curvature 0, are not treated as planar surfaces.
I tried to use all kinds of components in Grasshopper, like projection, rebuild, boundary surface, etc, no luck in fixing this.
Could anyone help me understand what is happening and how to fix this?
Haha, I know! It is weird. it is the first time I ran into this +0, -0, and 0 curvature not equal to flat.
Our client needs the final model to be in SketchUp format. Run into this issue during the testing. But curious to know why.
The other surfaces are not locked. I think this is a new feature in Rhino 8. For example, in ghost view Rhino 7, if you explode a box, all the surfaces will show isocurves. In Rhino 8, if you explode a box, none of the surfaces show isocurve. Until you run into this condition I described during modeling. This situation appears to be very random to me.