CGTalk - Tesselation problem

Mr. Brown

05-30-2002, 06:01 PM

let's say i want, for example, to model a tea cup.

i would build a curve then revolve it. i then duplicate the revolved surface, make it a bit smaller and place it inside the first (as in image1).

i then want to close these two surfaces with a little round shape. i tried to do it with fillets, with a birail, a torus, ... nothing will work. i tried increasing the object's tesselation, won't work neither (image2).

any suggestions?

Mr. Brown

05-30-2002, 06:02 PM

image 2

svenip

05-30-2002, 06:19 PM

at first : why don't you draw the whole curve as the profile and then revolve it ???

but anyway. good way here is to just attach both surfaces. you may need to take the top hull and put it in the right place, but thats not dramatic.

Mr. Brown

05-30-2002, 07:05 PM

but if i want to have a rounded shape on top? i know i could have drawn the whole curve directly if i wanted to do a tea cup. but it's a problem i'm having frequently and sometimes the only way to link to objects is with a birail or a fillet. that's why i was asking this question. how to fix or bipass the tesselation problem.

svenip

05-30-2002, 07:14 PM

hmm, ok. if you wanna do it by a freeform fillet e.g. you can go to the tesselation folder and switch on advanced tesselation. then play with the values for U and V. the higher the value the more the surface will be tesselated before rendering.

usually a value about 6 will give you a smooth result.

i tried that and it works.

Mr. Brown

05-30-2002, 07:42 PM

argh! not working. i've tried it with 6 just like you said. won't work. so i tried it with 20. won't work neither. argh!

exhibit A:

svenip

05-30-2002, 07:56 PM

so first it looks like the other two surface are not tesselated enough. but anyway. why not attach now the three surfaces and all will be gone. that's the usual way. always try to attach what's possible to attach.

another thing here is that the tangents are not aligned. means the top surface doesn't have the flat tangent on it's edge where it meats the revolved one. that's why you see the edge. again attach would solve.

Jhonus

05-31-2002, 12:47 AM

Originally posted by Mr. Brown
but if i want to have a rounded shape on top? i know i could have drawn the whole curve directly if i wanted to do a tea cup. but it's a problem i'm having frequently and sometimes the only way to link to objects is with a birail or a fillet. that's why i was asking this question. how to fix or bipass the tesselation problem.

I don't get it. Why can't you just draw the profile curve with a rounded top?

Anyway, for that sort of problem I usually just duplicate surface curve of the inner and outer rim, and then choose how i want to create the surface from there. Probably a loft. But for that you'll have to create a couple more curves in the middle so you can get the curved surface.

It should fit perfectly to your existing shape since it is built from it.

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