ExtendSrf (smooth, merge) of a trimmed surface automatically shrinks the resulting surface. This is not desirable if the user deliberately did not shrink the trimmed surface and expects the underlying surface of the extended trimmed surface to be the same as the trimmed surface before the extnsion (or an extension of that underlying surface.
Does McNeel believe it is imperative that the extended surface be automatically shrunk after the extension?
Example: ExtendSrfAutoShrink.3dm (2.2 MB)
The first extension of the trimmed surface coincides with the original untrimmed surface.
The second extension of the trimmed surface deviates from the original untrimmed surface.
No.
My question is whether McNeel believes it is imperative that the ExtendSrf command automatically shrink a surface after extending it. I’ll edit the post to make the question clearer.
Yeah I get that you think the shrinking is being done after the extend, but it looks to me that its being done before the extend. You can tell its done before because it won’t extend correctly past the first knot beyond any of the 4 edges of the surface. What would be the point of shrinking it after the extension other than to annoy users?
I suspect its done like this because it makes life easier for the developer.
My question was what do you mean by “imperitive”. It’s certainly possible to do it without shrinking. If McNeel says we would have to charge you more to hire people who can do it correctly is that a sufficient inperative?
It’s somethink like that, though my testing shows the limit is typically a bit past a knot line. And occasionally a trimmed surface can be extended a much larger distance. My guess is the algorithm has a number of enhancements/modifications/patches, added over the last 25 years or so to handle various situations, which are not entirely consistent with each other.
An attempt to politely inquire if there is a signficant reason for the shrinking.
I didn’t know extend edge of trim surface will shrink/ change the surface until now. Thanks for finding out. I would avoid extend surface edge of trimmed surface and modify the trim curve ( we call it COS in Alias) instead, and I think trimmed surface boundary is limited by that COS so extending trimmed surface edge doesn’t make sense, thats the original concept of “trimmed surface”
Extending a surface does not change the shape of the original portion of the surface. That is true whether the input surface is trimmed or not trimmed.
I don’t know what you mean. There are many reasons why a user may need to extend a trimmed surface.
That is another approach which I have used. But as I said above there can be reasons to simply extend the trimmed surface.
