Loft Issue

Today I tried to create a loft with 3 sections, all created with arcs connected.
The result is not what I expected, so I tried rebuilding the sections, and then the result was good.
It seems like a bug to me.

Loft Issue.3dm (438.9 KB)

If I loft the curves and change the options to refit, it looks like the rebuilt curves. Does that give you what you want?

Hi Joaquin- the point weights in the input curves are all different, and Loft is one of the commands that pays attention to the input curve structure. Rebuilding, among other things sets all the weights in the new curves to 1 (non-rational).


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Thanks Michael and Pascal,

Now I understand, I have already realized that rebuilding during the command like Michael or the way I did prevents the issue, but I didn’t understand why. Now it’s all clear.
Thanks for the quick answer.

TIP: if you made the second and third curves with an offset from the first, you probably got a more complex result. You can fix this two different ways

  1. Edit → Rebuild, then change the number of control points [try to match the same number as the first]
  2. Curve → Offset, then lower the tolerance [larger number / less decimal places]

Hi Dave,
Should this not be “increase the tolerance” as you want to allow for more tolerance?

This always is hard to explain! I’ll give you two examples.

High tolerance = 0.0001 (very small number)
Low tolerance = 0.1 (larger number)

So, to lower the tolerance & make it ‘less accurate / more simple / fewer control points’ we need to use a larger number. Going from high tolerance to low tolerance, you then need to use a larger number.


I would reverse that, myself. But, I guess I have a low tolerance for potential ambiguity in this- we need to standardize before we confuse everyone!!!


Nerd humor, love it!

It reminds me of photography…“you need more light, so open up the the aperture by using a smaller f-stop.”

Typical answer, “w-h-a-a-a-a-t-t?”

Hi Dave - I do think you are mistaken in how this is normally used -

Low tolerance = not much tolerance for ambiguity = small numbers = ‘tight tolerance’ = fastener fits the hole snugly

High tolerance = I can tolerate a lot of ambiguity = large numbers = ‘relaxed/loose tolerance’ = fastener may fit in the hole loosely and rattle around

You seem to interpret Low/High as a kind of rating on the standards in the tolerance, right? That is the ambiguity…


That is indeed my thinking:

When the tolerance is a larger number the tolerance is increased; I tolerate more; larger gaps, less continuity.

When the tolerance is a smaller number the tolerance is lowered; I tolerate less; smaller gaps more continuity.



Hey, thanks for the clarification. You are right; my terminology was not the best. I like the descriptors you used better, so I will use them from now on. Excellent explanation.

I think focusing on ‘tight’ vs. ‘loose’ first is the way to go, then mention the values that are required,

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As long as we’re all on the same page - (especially when it’s my page!)