Updating mesh of TubeGeometry object

[themaninblue]

Hi, I'm trying to create an animated tube, like a line that's being drawn live. This involves adding new points to an existing path and then redrawing the object so that it looks like it's being drawn.

However, I've struck a problem with the tube object I'm using: when I update the path points the mesh object doesn't update on the screen, so it seems like I can't modify it after it's been created.

My 3d object creation is roughly like this:

var curve = new THREE.SplineCurve3([new THREE.Vector3(x, y, z)]);
var geometry = new THREE.TubeGeometry(curve, segments, 2, radiusSegments, closed);
geometry.dynamic = true;
var tubeMesh = THREE.SceneUtils.createMultiMaterialObject(geometry, [new THREE.MeshBasicMaterial({color: 0xffffff, opacity: 1, transparent: true})]);
scene.add(tubeMesh);

And when I want to add to the path I'm doing it like this (but it seems a bit hacky so I'm open to other ways):

tubeMesh.children[0].geometry.path.points.push(new THREE.Vector3(x, y, z));
tubeMesh.children[0].geometry.verticesNeedUpdate = true;

However, when I make changes the object doesn't seem to update on screen. Is it possible to do this with a Tube?

[mrdoob]

Do you know the full path of the line right from the start of the animation?

[themaninblue]

No, it's dynamically generated throughout the duration of the piece.

[mrdoob]

Well, then you can try doing a silly hack...

Generate a spline with the max number of points. Then... for the first frame you're going to display line from point 0 and 1, the rest of the points are in the same position as 1. Then on the next frame you're displaying 0, 1 and 2, the rest of the points will be in the same position as 2, ...

Crappy, but maybe it does the trick?

[WestLangley]

Have you read about the limitations on buffer-resizing?

https://github.com/mrdoob/three.js/wiki/Updates

[themaninblue]

Thanks for the tip. I gave it a go but it still doesn't seem to update.

I created a simple JSFiddle for what you suggested (@mrdoob). It pre-assigns the spline in a straight line and then each frame iteration should move successive points out diagonally:

http://jsfiddle.net/themaninblue/t8JBe/

But again, it doesn't seem to update.

One thing I noticed is that the splineCurve has a "needsUpdate" attribute, but when I set this to true it never seems to get set back to false, so maybe it's being ignored?

[zz85]

i think for most three geometry classes doesn't allow you change a generated mesh vertices for you, unless you do it yourself. i've an example here which changes vertices for parametric geometries, but here's some notes:

http://jsdo.it/zz85/rVta

1. geometry vertices length has to be the same
2. you will need to calculate the new vertices. either that, or
3. generate new geometry mesh vertices with the same length, with that its easier to transfer the new vertices value
4. update the mesh vertices, and set needsUpdate flag.

needsUpdate for splineCurve is only applied when you do a getPoint() after you change the parameters of that splineCurve. the reason it won't work here because the points from the curve, and TNB frames are already generated and wouldn't be updated. you might have to do some of the work (and incur some amount of cpu work too).

another approach, which i had an example somewhere i don't remember, is to recreate a new tube each time your spline changes.

[themaninblue]

Thanks for the help guys, I ended up using the Line class and creating a big vertex geometry which I could modify the points for gradually. Couldn't figure out how to get the TubeGeometry to update when I made changes.

[mrdoob]

#1979

[gitliuyudong]

I can change the vertices in the tubeGeometry(such as :tubeMesh.children[0].geometry.vertices[3].x = 100). But i want to change the path point position(x,y,z) in the tubeGeometry.(it seems like in the article of http://jsfiddle.net/themaninblue/t8JBe/).But it appears nothing(it does not work).please give me some advices...thank you!

[WestLangley]

@gitliuyudong

As stated in the guidelines, help requests should be directed to stackoverflow. This board is for bugs and feature requests.

[ricardomfcoelho]

@mrdoob Obrigado!

[zhubenjie]

You are very 6