Offset surface result

unhandled

(Akche001) #1

Since long time it was in my mind. I think I’m not asking too much. :slight_smile:


#2

You might try _MergeAllFaces after offsetting…

Won’t be exactly the same, but this is what happens:


(Akche001) #3

Hi! Mitch it is, I think. Yeah, after merging faces. I’m sorry, I didn’t elaborate whole thing. I mean, can the edges be split vertex to vertex, as it is in result which I suggested. In fact to get this result, I merged all faces at once and then I split each Individually. I don’t know, but it seems more natural result than the one which is now.


#4

After merge you can split manually.

The reason why this does not work as you wish, is because offsetting polygonal planar geometry using bisectors (your option) is not straight forward thing.

If you try to offset solid mesh/brep manually surface by surface for more complex planar geometries (i.e. valence n>3), you will see that offset surfaces corners do not meet at the same vertex after offset. Thus it requires some sort of other method like this to have almost good result

Planar offset like this only happens at situations like yours or situations like this:
https://www.researchgate.net/publication/220391061_The_focal_geometry_of_circular_and_conical_meshes

For more complex geometries, this was even a paper about mesh offset and the code behind is not shared by this party:


(John Brock) #5

TestOffsetPolysurf with the Solid option on will result in what Mitch showed with MergeAllFaces.

To get 5 separate objects like you are showing will not be automatic.
To get your desired result, offset your original 5 sided curve, explode the resulting polycurves, then Loft each pair of parallel lines.


#6

In which rhino version this option exists?
I have current candidate 2 version of Rhino 6 BETA
(6.0.18012.13241, 12/01/2018)

And this function is not included.


(Akche001) #7

I also have same question.


(John Brock) #8

TestOffsetPolysurf is in V6.

It’s an incomplete “test” command so it’s name does not autocomplete and is not officially supported, not documented, but it’s handy in this case.

Test commands are a way for us to test ideas, concepts and new features before making new commands or adding new functionality to existing commands. The development was not finished to get this one into V6.


(Akche001) #9

Yeah, I understood what you mean, Many times offset surface even fail as it is in first example, other one is a simple roof which I often make and get this result, which need extra merge face click.


(Michael Pryor) #10

In cases like you are showing the Shell command is very useful. You build first a closed solid, then set a thickness and select the faces to remove (at least one face has to be removed to shell)


(Akche001) #11

Yeah, shell option can do what you have shown, but my question is specific to offset surface, on surface joined at different angles. While offseting, to a solid brep, side face edges did not split the way it should have been.

I have workaround like this and it works for almost all cases.


(Akche001) #12

Hi John! Thanks for the heads up! This command is not present in RC (6.1.18023.13161, 23/01/2018). Looking forward to check it out in future releases.


(John Brock) #13

Actually it is:
image


(Akche001) #14

Yes, I’m sorry. I used Testoffsetpolysrf instead of testoffsetpolysurface. Old habit! :roll_eyes: I tried it now and I get result.


#15

John
Is there a list of “Test” commands somewhere ,so we can all have a play.

i just tried test at my command prompt, all i get is “testpdfexport”, which bombed with a file does not exist error.

Phil B


(John Brock) #16

Sorry, no.
Test commands are a quiet way we can get proof-of-concept tools to users in an efficient manner. They are incomplete, not documented, preliminary, potentially buggy, unsupported, and generally short lived.
Think of test commands a pre-prototype tools. They exist as a way for us to involve customers with specific issues in the future solution.


#17

It’s a test command… It would be a great joy if Rhino managed to generate convincing and correct offset polysurface (especially keeping the edges sharp).