# SubD tapering - problems and suggestions

Hello, I have found myself needing to use a specific workflow for something to ensure tapering (draft angles with SubD).

Now, first problem is that ExtrudeCrvTapered will never made a SubD surface when using a SubD friendly curve. Can you please add the Output=SubD option to this tool as you can do with normal ExtrudeCrv?

Secondly, if I have a subD friendly curve and I offset it inwards (to move it up then SubDLoft between them) then the offset curve is not SubD friendly. Is there any way to make the offset curve to be SubD friendly? If I scale the curve in X+Y it would scale disproportionately so that is not an option.

I am sure someone will say “SubD isn’t intended to be used for parametric or accurate modelling” or whatever, but that’s my business and I think this would be easy to implement.

This is a rough idea of what I want to do (draft exaggerated). I also want to keep a fillet on that top edge but I will work that out otherwise.

Have you tried the ‘_-MakeSubDFriendly’ command?

I always get dreadful results using that. I considered trying it but it would still be an inefficient workflow and require you to calculate the inset value and how much you raised it by to get a draft angle in degrees.

I have tried and it really will not work this way. The original SubD friendly curve has 12 points, when I offset it the normal Crv has 105 points. If I rebuild with 12 points and MakeSubDFriendly turned on the geometry changes too much for it to be a draft. I am hoping ExtrudeCrvTapered could be given the subD output option unless this was somehow mathematically impossible?

I think I would use Offset Curve with the option Loose=Yes. That way at least you have the same control points on both curves…

Thank you, this does give a much better result, and interestingly using SubDLoft between the base curve which is SubD friendly and the offset curve (moved up in z direction) does result in a SubD surface.

As I said before though, to do it this way and calculate draft angle is a pain and it would be nice if there was a more efficient way. For now I will do this and as long as it is roughly 1.5-2 degrees of draft it will do the job.

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Ok… my next wish. So I have this drafted face which is what I want. Now I want to fill the top face with SubD surfaces (manually because the Fill command isn’t great here). So I want to crease these edges

Then use append face or even bridge to start filling it in. When I do that the edges become uncreased again and I have to add the creasing back in manually (which is time consuming/annoying):

Could it be made so that when I bridge here with the edge creased that it remembers that it is creased? This would help me get to where I want much quicker. What I want to do is fill the face and then bevel it (effectively fillet it) while still remaining entirely in SubD.

Example:

SubDSweep1 command is easier.

I have no idea what you think this shows. I know I can do that but you are not definining the draft angle mathematically there in any way as I have asked.

Good idea, this does actually work to do what I wanted. Hoping ExtrudeCrvTapered could have a SubD result added though.

Now trying to work out how best to do the second part I want to do.

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Yes, Andrew already posted the best solution and I said it worked. Better to do it with the full profile and 1 curve though - and this is still slow paced compared to most SubD modelling. SubD output needs to be added to ExtrudeCrvTapered.