TubeGeometry: Added parametric radius via THREE.Path.

[spite]

For variable radius along the tube geometry (like the old taper, but with more control using a Path). Still works with a number, and it should be serialisable.

[WestLangley]

Such a change will require a change to the computed normals, too.

[spite]

Right... might be easier to call .computeVertexNormals afterwards?

[WestLangley]

might be easier to call .computeVertexNormals afterwards?

That is a problem do to the seams -- in TubeBufferGeometry at least. The analytic solution would be best.

@Mugen87 I expect TubeBufferGeometry could be more carefully written to share vertices on the seams. There is the side seam -- and, if closed, the end seam.

[Mugen87]

Sharing vertices might cause problems with uv-coordinates. I'm not sure this approach will work for TubeBufferGeometry.

[WestLangley]

Rats. I forgot TubeBufferGeometry supports uvs.

So the solution must be the analytic one.

[spite]

This is the current code calling computeVertexNormals after the attributes are set.

EDIT: A more normal use, a tapered TubeBufferGeometry

And the current unmodified TubeBufferGeometry:

[WestLangley]

Yes, this is a cool feature. :-)

You should see a clearly-visible seam if you reduce radiusSegments to 6 and call computeVertexNormals(). Analytic normals do not have that problem.

You can also use VertexNormalsHelper to see the normals.

[spite]

I see

I'll see what can be done. It's not too terrible since path can be sampled around the segment point...

[WestLangley]

@spite

How about specifying radius as a simple function defined on [ 0, 1 ], instead? That is what I did.

Here is my hack to compute the adjusted normal.

var P = new Vector3();
var P1 = new Vector3();
var P2 = new Vector3();

...

// normal

normal.x = ( cos * N.x + sin * B.x );
normal.y = ( cos * N.y + sin * B.y );
normal.z = ( cos * N.z + sin * B.z );
normal.normalize();

if ( radius instanceof Function ) {

	var delta = 0.0001;
	var t1 = i / tubularSegments - delta;
	var t2 = i / tubularSegments + delta;

	// Capping in case of danger

	if ( t1 < 0 ) t1 = 0;
	if ( t2 > 1 ) t2 = 1;

	P1 = path.getPointAt( t1, P1 );
	P2 = path.getPointAt( t2, P2 );
	var delta = P1.distanceTo( P2 );

	var r1 = radius( t1 );
	var r2 = radius( t2 );

	normal.addScaledVector( T, - ( r2 - r1 ) / delta ).normalize();

}

[WestLangley]

@Mugen87 This pattern is unfortunate...

P1 = path.getPointAt( t1, P1 );

If the function accepts a target, it can be

path.getPointAt( t1, P1 );

If not, then it must be

P1 = path.getPointAt( t1 );

So we have to write it to accommodate both...

[spite]

@WestLangley my version of this takes a number or a function as radius, but @mrdoob said it couldn't be like that because it couldn't be serialised. So I have another version which takes an array of values, but that's cumbersome. Path has the most flexibility of all

[WestLangley]

@spite OK. The math I posted to compute the normal can be easily modified to accommodate Path. I expect you can make it more efficient...

[spite]

Seems about right now: a hairy pipe thingie

[Mugen87]

We still have to adjust the documentation of TubeGeometry and TubeBufferGeometry

[AGuyCoding]

will this be ever merged in the master?

[Mugen87]

The PR is not yet complete since it's also necessary to add serialization/deserialization and update the docs/TS file. Besides, I'm not sure we really need this feature. In the meanwhile, I tend to keep the geometry generators as simple as possible. @mrdoob has to decide what he prefers.

[spite]

@benjaminadrom do what i do if you really need that feature: import it as another type of Geometry (like ParametricTubeGeometry) and use it instead of the default TubeGeometry

[AGuyCoding]

@benjaminadrom do what i do if you really need that feature: import it as another type of Geometry (like ParametricTubeGeometry) and use it instead of the default TubeGeometry

Thanks a lot for your suggestion,
did you mean "ParametricGeometries"? I can't find a "ParametricTubeGeometry" as you said.
May I ask you for a little guidance for "ParametricGeometries" + taper?

[Mugen87]

I can't find a "ParametricTubeGeometry" as you said.

The idea was that you create yourself a custom class with the code from this PR.

[Mugen87]

taper was removed on purpose and I don't think we should it add it back or an advanced version of it. The idea was to keep the generators simple/compact and not enhance them with many features. Otherwise one could argue that variable radii could be added to CylinderGeometry and torus geometries, too. This would get quickly out of hand.