SketchUp is not a NURBS modeler because...

thomthom

Patches generate regular geometry which is much easier to map as you know the full structure of the mesh.

Pixero

Something like this:

Absolutly!

Is it Nurbs or splines or what?

thomthom

Bezier patch.
I was thinking that if you could assemble a Bezier surface of Quad and Tri patches you can shape most things.
Currently it has the 16 control points, but I kind of want a simpler one, with just the corner control points with handles. But I guess there can be use for both...

fredo6

3D Nurbs are possible in SU in theory, but requires to interface the script with a C library in order to get decent performance for preview and edition. That's of course possible, but a long work, especially for merging two nurbs surfaces.

Indeed, it would help if the SU team would fix the bug which prevents surfaces to be drawn in any other color than gray or black (as you can see in Curviloft).

Note that Nurbs would not always answer the problems of the real world when you wish to have given contours, with strict dimensions. Most 3D modelers use numerous techniques to manage this, not just Nurbs.

I may one day do something with Nurbs, but I am also exploring alternate techniques that may give acceptable results in some frequent situations. For instance, I am playing with surface generation from contours (not necessary horizontal), as shown on the picture below. This is not based on Nurbs, but I think it will give a more realistic shape when modelling a terrain.

Fredo

Topo Gradient 2.skp

thomthom

@unknownuser said:

3D Nurbs are possible in SU in theory, but requires to interface the script with a C library in order to get decent performance for preview and edition.

You mean deforming it live? Is the calculation that expensive? If it's just applying the transforming that consumes time I don't think moving to C will do much.

For Vertex Tools I wrote the soft selection code in C. What I found took a lot of time was casting the Ruby values to C data types - so much in face that doing a prepass of converting the whole 3d point data set first before processing it gained a great amount of speed.

I'm currently working on a Bezier Surface system where you add quad and tri patches together. At the moment it all in experimental stage - but as it matures I might port some of it to C if I find a lot of the calculation to be very consuming. Though often I find the bottleneck to be SU's methods of adding geometry.

And I'm also trying to get to grips with B-Splines - I've never worked much with them. But when I read about Bezier curves I often see them mentioned - that they can be more intuitive to control?

pilou

Maybe this can interest you

mitcorb

@Pilou:
Look out. The Phonetians might put a bounty on your head for besmirching their prophet.

pilou

@Mitcorb

P Bezier was a funny guy!

Very very interesting site!! (I have crossed Ergun AKleman for Topmod: French version
Site of Topmod is now on "Stand by"
you can just load the prog!
A very special but absolutly terrific program!
Here the last version of TopMod
Here computer aided caricature
P Bezier By Ergun Akleman

By me with Topmod