I am working with solids and don’t understand the behavior of the control points. For instance when I moved the control point marked in green downwards it created a concave surface (marked in blue). Shouldn’t the surface remain flat (marked in red).
Also, when I pushed the outer control point down it pushed the inner one down too. But when I only pushed the inner one down the outer one did not get pushed down.
Hi Justin - the point you moved is not really control point in the way it is usually meant in Rhino - control points are not available for joined surfaces. What you moved is a ‘SolidPt’ and the reason it does what it does is that the top face oh that object is not radial but a trimmed plane. ExtractSrf the top of the original and turn on control points (f10) to see this.
What you’d need here is a radial surface (which you can get by lofting the two top edges together and replacing the trimmed plane with that in the polysurface.)
Editing Solids in Rhino by moving vertices, edges, faces or via _solidPtOn is a bit limited.
And sometimes / many times unexpected as you experienced.
And not a typical Modelling-Workflow in Rhino.
Rhino is more a Surface Modeller or also called explicit CAD. The feature you re after is more common in Solid-Modeller / implicit CAD / feature Tree Modelling.
explaination
the underlaying surfaces also explain the behaviour you’ve seen:
i added an example that behaves like you wanted:
_extactSrf and _untrimAll (the surfaces in the back )
at the left you are deforming a single squar-like surface - and deform it to the concave one to the right.
the surfaces, as part of the polysurface / Brep, was a trimmed surface.
at the right, the surfaces is build as revolve and is untrimmed.
it deforms as you expected.
if you need a surface of revolution to be adaptable, the most powerful approach in Rhino would be to draw a closed curve, turn on history, do the _revolve.
now modifying the curve will also modify the surface / solid.
(EDIT: @jim@Justin_ID I added the headlines to make my answer more clear)
Sure a Surface of Revolution is the correct Solution for this users problem, but why not just tell the user how to go directly to that end solution?
No, what you did was join in on the stupidity.
There is no simpler easier way to make what the user wants than to revolve the curve that produces the result he wants.
If you are after rock solid geometry, perhaps you should consider this → the best and most robust way to make Solids in Rhino is to NOT use the solid tools. Rhino’s surface modeling tools are far more capable of making valid solids that you can reliably export to other solid modeling CAD programs than the Rhino Solid Tools can.
I read my answer again and I do not see any stupidity. ( I will add headlines to make it more clear)
Justin asked why the surface is getting concave, I pointed out there is a limitation on Solid-Editing and explained the concave result
So is it safe to say that when an enclosed polysurface (solid) is constructed without any trimmed surfaces it will behave more predictably when trying to edit it with SolidPt or solid edge manipulation?
And because some of the in-built solids tools automatically build solids with trimmed surfaces they don’t lend themselves to downstream solid editing tools?
Fool that I am I was trying to help the user undestand why the thing he has behaves as it does, which after all is what he was asking, not how to make a different thing. Somehow I guess I just knew you’d be there to take on that task, thanks so much.
Rhino is not a parametric solids modeler like SolidWorks or Inventor.
It appears you are expecting parametric functionality, and that would explain why you feel there are problems.
