Aberations denoting a twisted mess atop surface not evident in analyze


Aberations on surface shaded view.3dm (831.9 KB)

why is this ?

I have meshes custom slider fully maxed to right


Your “front” side surface has 4 rows of control points stacked on top of each other at the edge. That is causing the meshes to go nuts at the joint. I don’t know how the surface got that way, perhaps you need to re-make it. The rear side surface seems OK.


Hi @Steve1, I deal with stacked control points on edges often.
See the files below where I’ve removed them.
This should show up ok now. Michael VS
Aberations on surface shaded view_RH4.3dm (954.3 KB)
Aberations on surface shaded view.3dm (774.2 KB)

I have opened the two 3dm files and selected the blue curve at that edge and turned on control points, I see no difference between one imported from my file and your fixed file.

Any chance of a printscreen showing where they reside and what curve. Are they control points for the blue rail I used or are they control points in the resulting surface edge ?

I created the surface by using DupEdge on the edge of the radiused edge and the other two gentle curves, ditto method stbd side, fault being port side. so why no issue with same method stbd ?

I have not come across this before and stacked control points are new to me, so I need to know what they are, why they occur and how to fix them.

Is there a find stacked control points command ? Like that for naked edges ?



Hello @Steve1, In our inhouse hull design software stacked control points are common on edges when Iges are imported into Rhino. I’ve read that this is also common with hulls created using Maxsurf.
In the past I also had a hard time finding these stacked control points, because missing one can give you all sorts of problems later down the modeling pipeline, like surfaces that won’t trim or split etc.
In 2010 I had asked about this on the old newsgroup and @pascal was kind enough to write me a script which helps to find these problem points.
FindStackedPoints.rvb (3.5 KB)
By dragging this onto Rhino it adds 2 x commands:
What you do with them once you find them can vary though…
I find using the RemoveControlPoints command useful for this but make sure you remove the right rows of points and check your surface shape after removing as sometimes the shape can change drastically.
If you get odd trim shapes during removal then Untrim your surface.
EDIT: I see Pascal has this script on his website too:
Michael VS

clicking on the FindStackedPoints.rvb link sees…
The page you requested doesn’t exist or is private.

on Pascals website I search on staked and it finds SelStacked

How can I get the StackedPoints command ?

just what are they and where, blue line in my file ?
It was created by DupEdge from the edge of a swept arc, so why has it got these ?, I see only one set of control points for it, so I can but assume stacked points are hiding perfectly one under the other ?



Can you post the file with exactly the curves you used to make the surface and a recipe to reproduce it? This sort of thing should not normally happen. – Mitch

Here is a plug-in version - give that a try - Drag and Drop onto your V5 to add


Slightly tested - I think it works.

StackedPoints.rhp (9.5 KB)


Hello @Steve1, I agree with Helvetosaur, this should not normally happen, and I haven’t seen it happen as a result of modeling in Rhino. My observation is that it is often present on Surfaces imported from Iges files.
That said… Yes. Stacked points are 2 or more control points which are normally on the edge of the surface and occupy the same (Or within tolerance the same) point in space as one another. This confuses the Rhino mesher since it tried to join the dots so to speak and there are no spaces between them. This is normally visible by those shadowy edges in shaded mode.
If you switch on control points for the surface(F10) and try to click on a stacked point you will see that instead of selecting the control point you get a list of control points to select. Highlighting over the list you can normally figure out which point is on the outside or inside by looking at the highlighted lines which join the control points as you highlight each one in the list. The highlighted link is normally to the nearest neighbour control point so eg. When you highlight the innermost control point then the CP neighbour highlight(Not sure what to call this) will highlight to the control point lying inside the surface. The other highlights won’t do this. So select those points, pull them away so they are easier to grab and then remove control points for that row. Fixed. Sometimes and Untrim is also necessary. Michael