Full Version: Creases when subdividing an extruded polyline triangle

Hi!

When subdividing a triangular prism (extruded polyline triangle) like this one



Then there are notable creases:



When separating the surfaces then you can see that the control points are not well set for curvature continuity.



Any chances to get rid of those crease?

There are no such creases when subdividing an extruded rectangle (box).

I'm using Max Smirnov's "Subdiv_beta9.zip".

Any feedback is highly appreciated!

TIA and best regards

Bernhard

Attachments:
prism.3dm

Image Attachments:
prism.png  subdividedprism.png  subdividedprismcontrolpoints.png 

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Hello,

On Max website, there is a script called : Subdiv Classic
http://moi.maxsm.net/item/33

It will apply a Catmull–Clark subdivion on you Moi model.
You can try to apply this subdivision 1 or 2 times before the applying the Subdiv conversion.
It should reduce the crease quite a lot.

Image Attachments:
SubdivClassic.jpg 

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Hi Bernhard, also you could try dividing it into Quads by trimming / joining it like this, and make sure the "High quality mode" checkbox is set:









- Michael

Image Attachments:
Bernhard_subd1.jpg  Bernhard_subd2.jpg  Bernhard_subd3.jpg  Bernhard_subd4.jpg 

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Hi PaQ,

Thanks very much for the fast response. Sounds very promising. The triangle is part of a much more complex model, so I'm curious how the classic subdivision will play along. I'll try it out a report how it goes.

best regards

Bernhard

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Hi Michael,

Thanks very much for the hint! I'll try it out. From what I can see, the resulting shape will be slightly different when applying this solution. Nevertheless, I'll give it a try and report if it can be applied for my use case.

best regards

Bernhard

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Hi!

It turned out that the triangular prisms integrated in my model are not causing visible creases (lucky me).

Nevertheless, thanks again for the hints - I'm having the feeling that this knowledge is needed, sooner or later :-)

best regards

Bernhard



P.S.: it took me a while to figure out how to create a triangular prism that has control points: you need to loft two adjacent lines and then extrude the surface. When instead extruding a plane polygon triangle or lofting two polygon triangles (with closed caps), then you loose the control points (because the control points of the individual surfaces don't align).

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Interesting info, thanks PaQ and Michael. I didn't know yet that combining SubdivClassic with the regular Subdiv has its advantages.

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