I see that the result is different (PlanarSrf creates a trimmed surface with points beyond the surface), and EdgeSrf (a new command in my case, it seems to creat a sruface with points only along its edges) only works if a polyline surface-boundary-to-be is exploded first. I don’t really understand the difference between these things. It would be great to be able to fully understand that, and the utility of each of the two different resulting objects.
EdgeSrf is typically not for planar surfaces.
If you create it from curves that are of higher degree, it will create a surface that respects that too. Should we add that info to the help file too?
PlanarSrf:
Works only with input curves which are coplanar.
Result is a trimmed plane.
Input curves need to be coplanar and form a closed loop.
Any number and type of input curves.
EdgeSrf:
Works with non-planar input curves.
Result is an untrimmed surface.
Input needs to be 2, 3 or 4 open curves.
Input curves do not need to be coplanar.
Input curves can be any degree
If the input curves form a closed loop then the resulting surface will exactly match the input curves.
If the input curves do not form a closed loop then the result will be a surface which does not match the input curves but uses a sort of “average” position.
The degrees and numbers of control points of the resulting surface will depend on the degrees and numbers of control points of the input curves.
If the input curves are smooth the resulting surface will be smooth.
If the input curves contain kinks the resulting surface will be creased.
PlanarSrf also creates a surface with edges which match higher degree curves, but a trimmed surface.
That is because the input to EdgeSrf needs to be 2, 3 or 4 distinct curves, not a polycurve.
sure, they will match them, in fact the edges are identical to the curves, but the surface itself is a plane surface of degree 1
Thanks for all that info.
I had to use EdgeSrf to create a planar surface to use as a base surface for a FlowAlongSrf operation, because PlanarSrf gave me a surface with points beyond its boundary (a trimmed surface). So that’s one instance where an untrimmed surface was required and a trimmed surface would not do.
If for a moment we restrict the discussion to a surface which is planar, I’d love to understand the different uses if the surfaces are trimmed vs untrimmed.
I’ve been using Rhino daily for several years now, joining surfaces and making planar snd nonplanar surfaces and trimming and exploding and sweeping etc, and never paid any attention to whether the surfaces are trimmed or not. I didn’t even notice that an object could display two types of points (Solidpts vs F10).
In general untrimmed surfaces are always preferable to trimmed surfaces for multiple reasons if an untrimmed surface can be used. With planar surfaces compared to non-planar surfaces the advantages of untrimmed surfaces are reduced.
Some of the advantages of untrimmed surfaces include:
Improved accuracy in some situations.
MatchSrf only works with untrimmed edges.
Direct control over the shape of the edges by manipulating the surface edge control points.
Edge curves untrimmed non-planar surfaces will generally have few control points than the edges of trimmed non-planar surfaces.
Flow and similar commands are simpler to use with untrimmed surfaces.
Solid points only exist for polysurfaces and solids, and have limited capabilities compared to control points (and edit points for curves).