Proposal for Expansion(Grow) tools rather than Scaling(Stretch) tools

I have a dilemma. This dilemma is almost 2 decades old now. In fact this dilemma is probably at least 6,000 yrs old.

Long story short, make a truncated cone approximately 6 inches in size, with a side angle of say 45 degrees; shelled out to a wall thickness of a ratio of about 1.5% of its overall size – just guess. For example, if the overall size of this object is 6 inches, then use wall thickness of approximately 80 thousandths of an inch.

Now, “scale” said object X,Y and not Z. And do this “scaling” without the shell walls changing angle and thickness.

That’s the dilemma.

From everything I’ve discerned about Rhino’s transformation tools, they all “stretch space” rather than “expand space”.

I would like tools that “expand space”. But maybe the words I should use is “grow space”?

There might be a simpler way of describing this dilemma.

I’m trying to keep it simple for now.

I might need to set something up in GH for further study…

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Depending on how you create the cone, you can use push/pull…

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Well, you can’t scale a truncated cone in XY and not Z without changing its angle - try it on a non-thicknessed cone surface. Basically you need to Offset the truncated cone edges in XY by the same linear amount top and bottom to keep the same angle. Not the same thing as scaling.

This sounds very parametric to me, so I think that GH is the main Rhino-based solution for now.


Hi @lander,

Rhino’s Scale commands use affine transformations to modify geometry. So, these commands on their own will not help you achieve your goal.

– Dale

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Indeed, very true. I wish there were some other option since ‘scaling’ seems to just stretch space – maybe GH is perfect for this.

I’ve imagined how to solve this dilemma for about 19 yrs. And yes I’ve always wanted to focus on solutions for this in ‘parametrics’, and yes I’ve made a fare amount of files for this in programs like Alibre Design, CATIA, etc.

But I’ve always wanted to look at it from an organic perspective where a possible ‘cellular growth’ aspect can be applied to it like nature does, where cells divide and pop into existence or particles pop into existence – thereby expanding spacetime rather than stretching space…

very interesting :face_with_monocle: :thinking: :thought_balloon:

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Hello- it’s hard to tell but sounds like maybe what you want is features - a cone that knows it is a cone - an offset or wall thickness that knows its value and matains it whatever you do with the cone.
Rhino touches on this stuff in GH and slightly, here and there, in plain Rhino, and cerainly it could incorporate some of this some more, but is not a feature-based modeler.


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If you want to do that just explode the truncated cone and scale3d just the cone part and then createsolid to turn it back into a truncated cone.
truncatedCone.3dm (99.4 KB)

There is no need to spend 19 years pondering how to do this…


I appreciate your ponderings. And the ponderings of others on this matter. It’s understandable that no one should have to struggle on this type of dilemma for 19yrs or more.

Yes it seems to be a matter of ‘parametric features’ etc., so I’m grateful to look forward to spending more time with Grasshopper during my further ponderings of this.

In the meantime its good to know of the “affine transformations” characteristics – it puts a name to it I suppose.

I’ve always wondered how Rhino could enlarge things in different directions, but rather in a way that doesn’t “stretch” stuff out and distort angles.

If only we could “grow” geometry instead of stretch or distort. Maybe I can learn more how GH could do this, not only in a simple feature based way, but maybe some complicated particle physics based way.

Yes, for now I’m trying to share this dilemma with others in the simplest way possible, but trust me my underlying problem(s) relative to this are actually ever more complicated.

I might not be able to share everything exactly, but I will try to do it in a way that might benefit all users of Rhino and GH.

@jim just sharing what I see in your file:

I like what I see here, meanwhile this is merely a foundational exercise to what I will share next.

Bare with me, if this seems tedious at first. :beers:

The next things to come, will be features derived from more of a ‘loft’ shape in the long run.

The cone shape, is merely the simplest way to convey somewhat sensitive design geometries per say.

I’ll try to make this more interesting soon, with some added details to the challenging aspects of this matter.

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Of course if you plan stuff like this in advance, you don’t even need GH. Of course this only works with simple examples like a cone…


That’s pretty cool though, you must be using history and push pull :blush:

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No push-pull, this is V7, just a simple revolve of a closed profile with history on.

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Cool. It’s interesting how you can move the lines of the profile without edit points turned on etc.

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Sub-object selection…

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