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Extrude a shape along customized curve

Fantashit January 6, 2021 1 Comment

Description of the problem

I integrated a de Boor algorithm + casteljau (bez segments) Curve toolkit into my system (also I have different R. V. distributions implementation to generate control points smartly), which generates curve points adaptively. Now I want to extrude a shape (a series of points, not what three.js default extras/core/Curve.js defined objects), rectangles for example, along a curve, to draw lanes.

All my geometric level data are generated by parameter server (Topological Level) using Half edge based infrastructure. Hence for some well known reasons, I just use three.js for drawing in browser side, and I cannot use any algorithms provided by three.js, like quickhull, to perform computation.

As far as I know, three.js provides me ExtrudeGeomtry. But it uses three’s Curve. I want to extrude a shape along a curve (a series of points or Vector3 instances) instead of /core/Curve object.

Question

Is it possible to extend a shape from array of points or Vector3 instances?

Features 1

As far as I know, three.js provides me ExtrudeGeomtry. But it uses three’s Curve object. I want to extrude a shape along a curve (a series of points or Vector3 instances) instead of /core/Curve object.

Is it possible to extend a shape from array of points or Vector3 instances? Alternatively, if we can adapt a array of points into a Curve instance. It is good for me.

my current solution is drawing faces from scratch, but I think that it will be better if three makes customer curves easier to use.

Feature 2

Another problem is, I have concepts of curve segments internally. But I use it for navigation and location. What I need is?

(1) In which segment, the target is. Retrieve road info like speed limit, traffic signs, type (express?), etc.

(2) the segment is a whatever linked list, (what ever data structure you use), so that navigation can follow, retrace, and make decisions

Feature 3

If you want to check whether there is a hole in the geometry, simply use Euler-Poincare formula:

V - E + F - ( L - F ) = 2 ( S - G )

Three.js version

Browser

All of them
Chrome
Firefox
Internet Explorer

OS

Hardware Requirements (graphics card, VR Device, …)

Author: Fantashit

1 thought on “Extrude a shape along customized curve”

@yiakwy

Try this:

// Polyline3 class

function Polyline3( points ) {

	THREE.Curve.call( this );

	// points is an array of THREE.Vector3()

	this.points = points;

}

Polyline3.prototype = Object.create( THREE.Curve.prototype );
Polyline3.prototype.constructor = Polyline3;

// define the getPoint function for the subClass
Polyline3.prototype.getPoint = function ( t ) {

	// t is a float between 0 and 1

	var points = this.points;

	var d = ( points.length - 1 ) * t;

	var index1 = Math.floor( d );
	var index2 = ( index1 < points.length - 1 ) ? index1 + 1 : index1;

	var pt1 = points[ index1 ];
	var pt2 = points[ index2 ];

	var weight = d - index1;

	return new THREE.Vector3().copy( pt1 ).lerp( pt2, weight );

};

var path = new Polyline3( points );

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