三个JS Gridhelper Polar可能吗？

Question

I'm using Three JS and I can add a grid to the scene using the GridHelper . Is there similar functionality which produces a polar grid?

This is how the geometry for a 2D Cartesian plane is generated ( source ):

var geometry = new THREE.Geometry();
var material = new THREE.LineBasicMaterial({ vertexColors: THREE.VertexColors });

this.color1 = new THREE.Color(0x444444);
this.color2 = new THREE.Color(0x888888);

for (var i = -size; i <= size; i += step) {

    geometry.vertices.push(
        new THREE.Vector3(-size, 0, i), new THREE.Vector3(size, 0, i),
        new THREE.Vector3(i, 0, -size), new THREE.Vector3(i, 0, size)
    );

    var color = i === 0 ? this.color1 : this.color2;

    geometry.colors.push(color, color, color, color);

}

THREE.LineSegments.call(this, geometry, material);

I tried rewriting that as follows:

var segments = 64;
var material = new THREE.LineBasicMaterial({ color: 0x1976D2 });
//Somehow below didn't work...
//var material = new THREE.LineBasicMaterial({ vertexColors: THREE.VertexColors });

var geometry = new THREE.Geometry();

this.color1 = new THREE.Color(0x444444);
this.color2 = new THREE.Color(0x888888);

for (var i = -size; i <= size; i += step) {
    var circle = new THREE.CircleGeometry(i, segments);

    // Remove center vertex
    circle.vertices.shift();

    geometry.merge(circle);

    var color = i === 0 ? this.color1 : this.color2;

    geometry.colors.push(color, color, color, color);

}

THREE.LineSegments.call(this, geometry, material);

But somehow the lines are dashed...

Answer 1

Try some like this:

THREE.PolarHelper = function(radius, rStep, aStep, color) {

  var helper = new THREE.Mesh();

  function line(r, a, color) {
    var material = new THREE.LineBasicMaterial({ color: color });
    var geometry = new THREE.Geometry();
    geometry.vertices.push(
      new THREE.Vector3( Math.cos(a)*r, Math.sin(a)*r, 0 ),
      new THREE.Vector3( -Math.cos(a)*r, -Math.sin(a)*r, 0 )
    );
    return new THREE.Line( geometry, material );
  }

  function circle(r, color) {
    var curve = new THREE.EllipseCurve( 0,  0,  r, r, 0,  2 * Math.PI, false,   0 );
    var path = new THREE.Path( curve.getPoints( 72 ) );
    var geometry = path.createPointsGeometry( 72 );
    var material = new THREE.LineBasicMaterial( { color : color } );
    return new THREE.Line( geometry, material );
  }

  var d = radius/rStep;
  for (var r=1; r<=rStep; r++) {
    helper.add(circle(r*d, color));
  }

  d = Math.PI/aStep;
  for (var a=0; a<aStep; a++) {
    helper.add( line(radius, a*d, color) );
  }

  return helper;
}

[ https://jsfiddle.net/tzsd5cre/ ]

Answer 2

It is dashed because you use THREE.LineSegments . This class connects every two subsequent points with as line. So if you want a continuous line you need to duplicate the points in the middle.

To explain it here an example:

v1 = new THREE.Vector3( 0, 0, 0 );
v2 = new THREE.Vector3( 10, 0, 0 );
v3 = new THREE.Vector3( 20, 0, 0 );
v4 = new THREE.Vector3( 30, 0, 0 );

Now if you make a line geometry using these points:

geometry = new THREE.Geometry();
geometry.vertices.push( v1, v2, v3, v4 );

line = new THREE.LineSegments( geometry );

It will look like this:

.__.  .__.
1  2  3  4

If you do :

geometry = new THREE.Geometry();
geometry.vertices.push( v1, v2, v2, v3, v3, v4 );

line = new THREE.LineSegments( geometry );

it will look like this:

.__.__.__.
1  2  3  4

The THREE.Line behaves differently and will connect all vertices with a continuous line instead. So this might be more like what you expected:

geometry = new THREE.Geometry();
geometry.vertices.push( v1, v2, v3, v4 );

line = new THREE.Line( geometry );

Will draw a continuous line connecting the points from the vertices array:

.__.__.__.
1  2  3  4