moving particles on face of imported *.obj in threejs

问题

I'm uploading via dat.gui a 3D *.obj (e.g. a cube) with 8 vertices and 6 faces (vertex indices). Although I can successfully move my points to the vertices, I cannot evenly distribute them on the faces of the model.

This is my process so far:

(1) LOAD OBJECT FILE

The example *.obj is quite simple:

v 5.526871 -3.827843 1.523720
v 5.526871 -1.827843 1.523720
v 5.526871 -3.827843 -0.476280
v 5.526871 -1.827843 -0.476280
v 7.526871 -3.827843 1.523720
v 7.526871 -1.827843 1.523720
v 7.526871 -3.827843 -0.476280
v 7.526871 -1.827843 -0.476280
s off
f 2 4 3 1
f 4 8 7 3
f 8 6 5 7
f 6 2 1 5
f 1 3 7 5
f 6 8 4 2

(2) TRIM ITS VERTICES & FACES

I'm using RegEx patterns to trim the vertices and faces and then push them to my geometry.

var faces_pattern1 = /f( +[\d]+)( [\d]+)( [\d]+)( [\d]+)?/g; // f vertex vertex vertex ...
if ( (result = faces_pattern1.exec(line) ) !== null ) {
   faces_pattern1.exec(line); 
   if ( result[ 4 ] === undefined ) {
        faces1.push( [
            parseInt( result[ 1 ] ) - 1,
            parseInt( result[ 2 ] ) - 1,
            parseInt( result[ 3 ] ) - 1
        ] );
    } else {
        faces1.push( [
            parseInt( result[ 1 ] ) - 1,
            parseInt( result[ 2 ] ) - 1,
            parseInt( result[ 3 ] ) - 1,
            parseInt( result[ 4 ] ) - 1
         ] );
    }
}
// push faces to geometry
for (var i = 0; i < faces1.length; i++) {
    this.renderer.geometry.faces.push( new THREE.Face3( faces1[i][0], faces1[i][1], faces1[i][2], faces1[i][3] ) );
}

(3) MOVE PARTICLES ON VERTICES

I have a number of particles, which i position to the vertices. This works fine.

var lg = allParticle.length;
for( var i = 0; i < lg; i++ ){
    var p = allParticle[i];
    p.diffX = ( vertices[h][0] * scale - p.x );
    p.diffY = ( -vertices[h][1] * scale - p.y );
    p.diffZ = ( -vertices[h][2] * scale - p.z );
    h += 1;
    if( h > nbVertices - 1 ) h = 0;
}

(4) DISTRIBUTE PARTICLES ON FACES

I now have a toggle, where i want to evenly spread the same particles on the faces of the cube. I try to do this using GeometryUtils.randomPointsInGeometry

var randomPointPositions = THREE.GeometryUtils.randomPointsInGeometry( this.renderer.geometry, lg  );
this.renderer.geometry.computeBoundingBox();
for( var i = 0; i < randomPointPositions.length; i++ ){

  var p = allParticle[i];
  p.diffX = randomPointPositions[i].x * scale ;
  p.diffY = randomPointPositions[i].y * scale;
  p.diffZ = randomPointPositions[i].z * scale ;
}

This distributes the points only on the x axis and not evenly on the area of the face. Any clues?

-- These are the faces (THREE.Face3) I'm getting:

{a: 1, b: 3, c: 2, normal: T…E.Vector3, vertexNormals: Array[0]…}
{a: 3, b: 7, c: 6, normal: T…E.Vector3, vertexNormals: Array[0]…}
{a: 7, b: 5, c: 4, normal: T…E.Vector3, vertexNormals: Array[0]…}
{a: 5, b: 1, c: 0, normal: T…E.Vector3, vertexNormals: Array[0]…}
{a: 0, b: 2, c: 6, normal: T…E.Vector3, vertexNormals: Array[0]…}
{a: 5, b: 7, c: 3, normal: T…E.Vector3, vertexNormals: Array[0]…}

Their calculated _area is always zero.

Similar question: THREE.js - position particles evenly on objects faces rather than verticies

回答1:

ok - it took me a while, but I solved it.

I tried the OBJLoader Method as suggested by G.Profenza.

Basically load the object, get its mesh, use the GeometryUtils.randomPointsinBufferGeometry and then move the particles to the vector3 you get:

OBJLoader: function() {
        var manager = new THREE.LoadingManager();
        manager.onProgress = function ( item, loaded, total ) {
            console.log( item, loaded, total );
        };

        var onProgress = function ( xhr ) {
            if ( xhr.lengthComputable ) {
                var percentComplete = xhr.loaded / xhr.total * 100;
                console.log( Math.round(percentComplete, 2) + '% downloaded' );
            }
        };

        var onError = function ( xhr ) {
            console.log ("ERROR", xhr);
        };

        var loader = new THREE.OBJLoader( manager );
        var allParticle = this.scene.getParticles();
        var lg = allParticle.length;
        var scale = this.renderer.scale;    
        loader.load( '/data/cube_02.obj', function ( object ) {
            object.traverse( function ( child ) {
            if ( child instanceof THREE.Mesh ) {
                console.log (" === CHILD === ");
                console.log (child.geometry);
                var randomPointPositions = THREE.GeometryUtils.randomPointsInBufferGeometry( child.geometry, lg  );


                console.log (randomPointPositions[0].x, randomPointPositions[0].y, randomPointPositions[0].z );


                for( var i = 0; i < randomPointPositions.length; i++ ){

                   var p = allParticle[i];
                   p.diffX = randomPointPositions[i].x * scale -p.x ;
                   p.diffY = randomPointPositions[i].y * scale -p.y;
                   p.diffZ = randomPointPositions[i].z * scale -p.z;
                }

            }

        } );


        //object.position.y = - 95;
        //this.renderer.sceneGL.add(object);

        }, onProgress, onError );



    }

来源：https://stackoverflow.com/questions/36305961/moving-particles-on-face-of-imported-obj-in-threejs

标签

javascript

three.js