Tube from 3d points

[TiagoCavalcanteTrindade]

In this topic there is code for drawing a tube from a set of 2d points, but I need to draw from a set of 3d points, where the tube can’t be represented as a line in a 2d plane.

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I’m working in a open source project and we need to create tubes like Wolfram does.

Linked GitHub issue: https://github.com/Mathics3/mathics-threejs-backend/issues/39.

[prisoner849]

Hi!
If you need round “joints” between line segments, then create a capsule geometry and use it for segments

[hofk]

Maybe you can use some of it?

Curved2Geometry - a twofold curved geometry

Construction One defines with some 3D points the center curve and for some angles the orthogonal radial distances of the hull from these points. By specifying the maximum values, one determines the vertical and radial fineness of the representation. With a definition string of three characters one determines whether caps are to be generated and whether these are to be flat or smooth. The third character allows radial connection without seam or symmetrical geometry. For symmetrical geometry t…

[TiagoCavalcanteTrindade]

@prisoner849

If you need round “joints” between line segments, then create a capsule geometry and use it for segments

How would I do that?

[TiagoCavalcanteTrindade]

I’ll try it out. But I guess yes, that seems to create the curve from a set of 3d points.

[prisoner849]

@TiagoCavalcanteTrindade

How would I do that?

Get points from a THREE.Path() of two .absarc(), and use THREE.LatheGeometry
For example: Selective Bloom (parts of a single geometry)

function CapsuleGeom(R, L){

  let path = new THREE.Path();
  path.absarc(0, 0, R, Math.PI * 1.5, 0);
  path.absarc(0, L, R, 0, Math.PI * 0.5);
  
  let pts = path.getPoints(5);
  
  let g = new THREE.LatheBufferGeometry(pts);
  
  return g;
}

[TiagoCavalcanteTrindade]

@hofk I couldn’t use your code .

@prisoner849 I don’t understand, doesn’t Path can only be 2D? I mean, it can be shifted and rotated, but it will always be a line in a 2D plane. Isn’t it?

An [probably bad] idea I had with your other comment is betwen each two coordinates have a tube geometry, but that would be very slow.

Another idea is use LineGeometry? Can it looks more 3Dish?

[prisoner849]

@TiagoCavalcanteTrindade

I don’t understand, doesn’t Path can only be 2D? I mean, it can be shifted and rotated, but it will always be a line in a 2D plane. Isn’t it?

When you create a lathe geometry, you can translate, rotate and scale it at your will in 3D.

[TiagoCavalcanteTrindade]

What I want to say is that even if it be rotated, translated and scalled it still is a line in a 2d plane.

There is a plane which pass through any 3 points, but this is not true for every 4 points, what leads to even if we rotate and translate a set of 2d points, its plane won’t contain every possibility of a set of 4+ coordinates. But of course this is a start, as I guess the tubes are going to be <4 points a good part of the time.

[TiagoCavalcanteTrindade]

I saw a solution for the path here.

I made the end caps with half spheres.

If anyone is interested in the code, it is in this PR and is going to be merged soon was merged.