CGTalk - Help! With "Patch Modelling" (NURBS)

View Full Version : Help! With "Patch Modelling" (NURBS)

brianemsu2

07-03-2003, 06:12 AM

I am having problems figuring out which way to go in this "patch modelling" setup.
I have taken the source images with a grid drawn on the face for front/side comparison.
Now I just need to start drawing the curves for a multi-patch model, but I can't really figure out the best way to begin.
I started with EP curves, but abandoned those because editing them after drawing them was not as straight-forward as the CV curves.
I am curve snapping all of them together, but I don't know how to maintain tangency between curves that follow along a major line of the face.
I have included some images of the starting point I am at.
Please look them over and see if you have any suggestions on if I am doing everything right of not.

brianemsu2

07-03-2003, 06:14 AM

I'm not sure how to post more than one image at a time

plotz

07-03-2003, 02:23 PM

I couldn't really see the curves in your pictures too well, but...

I don't think you need worry about wire tangency. The wires you layout shouldn't be looked at as the final layout for your surfaces...but guides for fitting separate surfaces to the model.

So I'd reccommend just laying out your curves the way you need them to build the basic surfaces of the head.

Thos surfaces will then be split, rebuilt, etc. to better fit together. Then you adjust the tangency of your surfaces.

If you can you should check out the book: "Inspired 3D Modeling & Texture Mapping" by Tom Capizzi

It's got a great section on patch modeling that, while not step by step, gives you an idea of how to go from low complexity/accuracy to high complexity/accuracy.

Atwooki

07-03-2003, 11:14 PM

Create a loft from some curves (those that would generate the orb of the eye, for instance; fine-tune the surface, keeping history 'on'...
Then select the curve leading towards the surface that you want to be tangent to that surface, and shift select the lofted surface.

Then go: curves menu ---> project tangent (at the bottom)choose 'U' or 'V' depending on the surfaces direction: this can always be edited in the channel box later, by selecting the curve.

Atwooki

webster

07-03-2003, 11:56 PM

Tangency was for a long time a big head-ache for me.
But then somebody explained it to me, since then i got it.

Basically a surface build from curves (Also without curves) can only be tangent, if 4 CV (Two from one Curve, Two from the other) are all on one imaginary line.

In image "A" You can see the 4 points are on on imaginary line(you can see only 3, but the first on one curve and the last of the second curve have of course to be point-snapped so that the surface is closed). If You would duplicate and Loft them, the surface should be 100% Tangent.

In image "B" the points are not on on line, so the surface will never be tangent.

Hope You got it.

Also check the "Project Curve Tangency" - Function

CGTalk Moderation

01-13-2006, 08:01 PM

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.