I suspect it might have something to do with the orientation of the first and last point of the Bezierspline?

The algorithm I use to calculate the control points assumes that the path between any two points is a curve so even if you just use the first and last knot then you still get a banana shape.

1. // Banana shape
2. PVector[] knots = new PVector[] {
3.   new PVector(240,0,50),
4.   new PVector(240,0,300)
5.  };

If you want a linear shape then ignore the knots array and use

1. path = new P_LinearPath(new PVector(240,0,50), new PVector(240,0,300));

Thank you Quarks, that makes sense.

As a matter of fact, what I need is a curved quasilinear tube. I am visualizing a proton beam from a particle accelerator, and have profile data and position data at different points. The extrusion class seems perfect for this!

The image shows front, side and topview
Here are some examples of wireframes built with shape3d so far:



Can you give me any ideas for workarounds?

It's really a great library, thanks so much for your work on this!

Thanks
Andres

Can you give me any ideas for workarounds?

Not sure what the problem is, since as far as I can tell, the images seem OK?

They re not - I am just shifting the bend very far away, so it falls outside the pictureframe. It would be great to be able to work with a finite tube-shape...

I think I understand the problem.

You are getting kinks in the tube and are extending the tube so that they don't appear.

It would be useful if you could post the data you are using for the 'knot' array - the one demonstrating the problem so that I can try it out.

Hi Quarks

Thanks for waiting.
Here is some data:

drawing3d_04_fordemo_982.png

[0] [ 384.59537, 371.7944, 400.0 ]
[1] [ 380.5674, 404.59552, 200.0 ]
[2] [ 381.0578, 388.9037, 0.0 ]
[3] [ 388.46545, 382.21384, -200.0 ]
[4] [ 374.17596, 394.41937, -400.0 ]

drawing3d_04_fordemo_768.png

[0] [ 283.67587, 365.54272, 400.0 ]
[1] [ 310.68973, 408.51846, 200.0 ]
[2] [ 441.61844, 366.34668, 0.0 ]
[3] [ 441.45566, 369.7105, -200.0 ]
[4] [ 444.73032, 386.6793, -400.0 ]

drawing3d_04_fordemo_142.png

[0] [ 269.0887, 392.63324, 400.0 ]
[1] [ 661.0589, 435.4888, 200.0 ]
[2] [ 368.063, 402.8792, 0.0 ]
[3] [ 319.995, 363.16116, -200.0 ]
[4] [ 494.74356, 460.80603, -400.0 ]

Points of view are chosen to best show the effect, they are not the same in the 3 pictures.

Thanks for looking into this!
Cheers

Fantastic!
Works great now, thanks man!
It actually works best in V2.0b3. (V2.0b5 has some quirks, using MacOS 10.6.8, Java 1.6.0_35)
:)