mesh-collision

return the contact set between two 3d meshes in motion

example

var collide = require('mesh-collision');
var mat4 = require('gl-mat4');
var transformMat4 = require('gl-vec3/transformMat4');

var loop = require('frame-loop');
var lerp = require('mat4-interpolate');
var teapot = require('teapot');
var bunny = require('bunny');

var bodies = [
    {
        prev: mat4.create(),
        next: translate(mat4.create(), [-15,0,5]),
        cells: bunny.cells,
        positions: bunny.positions,
        velocity: translate(mat4.create(), [5,0,0])
    },
    {
        prev: mat4.create(),
        next: translate(mat4.create(), [0,0,10]),
        cells: teapot.cells,
        positions: teapot.positions,
        velocity: translate(mat4.create(), [0,0,-1.6])
    }
];
var tmpm = mat4.create();
var origin = [0,0,0];

var engine = loop({ fps: 10 }, function (dt) {
    for (var i = 0; i < bodies.length; i++) {
        var b = bodies[i];
        mat4.copy(b.prev, b.next);
        
        var endm = mat4.multiply(tmpm, b.next, b.velocity);
        lerp(b.next, b.next, endm, dt / 1000);
    }
    
    for (var i = 0; i < bodies.length - 1; i++) {
        for (var j = i + 1; j < bodies.length; j++) {
            var c = collide(bodies[i], bodies[j]);
            if (c) {
                console.log(c);
                engine.pause();
            }
        }
    }
});
engine.run();

function translate (out, xyz) { return mat4.translate(out, out, xyz) }

output:

{ mix: 0.7277780106077933,
  point: [ -1.070312, 0.234375, 0.0786932272210148 ],
  normal: [ -0.5790840193768065, -0.8026245943343034, 0.14302258238508114 ] }

method

var collision = require('mesh-collision')

var contact = collision(a, b)

Raycast from each point in a onto b.

a and b both must have these properties:

• next - a mat4 of the next position and rotation
• prev - a mat4 of the previous position and rotation
• positions - an array of [x,y,z] coordinate arrays
• cells - an array of arrays of indexes

The positions and cells array structures are compatible with simplicial-complex.

If there was not a collision, return null.

Otherwise return contact, an object with these properties:

• point - contact point as an [x,y,z]
• normal - contact normal as an [x,y,z]
• mix - the amount of linear interpolation (0 to 1) between prev and next where the collision occured.

The contact object is modeled after the contact set mentioned in the SPOOK paper but using mix instead of a penetration depth.

install

With npm do:

npm install mesh-collision

license

MIT