Doodle3D-Slicer/library/csg.js
2015-04-24 21:32:39 +02:00

596 lines
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JavaScript
Executable File

// Constructive Solid Geometry (CSG) is a modeling technique that uses Boolean
// operations like union and intersection to combine 3D solids. This library
// implements CSG operations on meshes elegantly and concisely using BSP trees,
// and is meant to serve as an easily understandable implementation of the
// algorithm. All edge cases involving overlapping coplanar polygons in both
// solids are correctly handled.
//
// Example usage:
//
// var cube = CSG.cube();
// var sphere = CSG.sphere({ radius: 1.3 });
// var polygons = cube.subtract(sphere).toPolygons();
//
// ## Implementation Details
//
// All CSG operations are implemented in terms of two functions, `clipTo()` and
// `invert()`, which remove parts of a BSP tree inside another BSP tree and swap
// solid and empty space, respectively. To find the union of `a` and `b`, we
// want to remove everything in `a` inside `b` and everything in `b` inside `a`,
// then combine polygons from `a` and `b` into one solid:
//
// a.clipTo(b);
// b.clipTo(a);
// a.build(b.allPolygons());
//
// The only tricky part is handling overlapping coplanar polygons in both trees.
// The code above keeps both copies, but we need to keep them in one tree and
// remove them in the other tree. To remove them from `b` we can clip the
// inverse of `b` against `a`. The code for union now looks like this:
//
// a.clipTo(b);
// b.clipTo(a);
// b.invert();
// b.clipTo(a);
// b.invert();
// a.build(b.allPolygons());
//
// Subtraction and intersection naturally follow from set operations. If
// union is `A | B`, subtraction is `A - B = ~(~A | B)` and intersection is
// `A & B = ~(~A | ~B)` where `~` is the complement operator.
//
// ## License
//
// Copyright (c) 2011 Evan Wallace (http://madebyevan.com/), under the MIT license.
// # class CSG
// Holds a binary space partition tree representing a 3D solid. Two solids can
// be combined using the `union()`, `subtract()`, and `intersect()` methods.
CSG = function() {
this.polygons = [];
};
// Construct a CSG solid from a list of `CSG.Polygon` instances.
CSG.fromPolygons = function(polygons) {
var csg = new CSG();
csg.polygons = polygons;
return csg;
};
CSG.prototype = {
clone: function() {
var csg = new CSG();
csg.polygons = this.polygons.map(function(p) { return p.clone(); });
return csg;
},
toPolygons: function() {
return this.polygons;
},
// Return a new CSG solid representing space in either this solid or in the
// solid `csg`. Neither this solid nor the solid `csg` are modified.
//
// A.union(B)
//
// +-------+ +-------+
// | | | |
// | A | | |
// | +--+----+ = | +----+
// +----+--+ | +----+ |
// | B | | |
// | | | |
// +-------+ +-------+
//
union: function(csg) {
var a = new CSG.Node(this.clone().polygons);
var b = new CSG.Node(csg.clone().polygons);
a.clipTo(b);
b.clipTo(a);
b.invert();
b.clipTo(a);
b.invert();
a.build(b.allPolygons());
return CSG.fromPolygons(a.allPolygons());
},
// Return a new CSG solid representing space in this solid but not in the
// solid `csg`. Neither this solid nor the solid `csg` are modified.
//
// A.subtract(B)
//
// +-------+ +-------+
// | | | |
// | A | | |
// | +--+----+ = | +--+
// +----+--+ | +----+
// | B |
// | |
// +-------+
//
subtract: function(csg) {
var a = new CSG.Node(this.clone().polygons);
var b = new CSG.Node(csg.clone().polygons);
a.invert();
a.clipTo(b);
b.clipTo(a);
b.invert();
b.clipTo(a);
b.invert();
a.build(b.allPolygons());
a.invert();
return CSG.fromPolygons(a.allPolygons());
},
// Return a new CSG solid representing space both this solid and in the
// solid `csg`. Neither this solid nor the solid `csg` are modified.
//
// A.intersect(B)
//
// +-------+
// | |
// | A |
// | +--+----+ = +--+
// +----+--+ | +--+
// | B |
// | |
// +-------+
//
intersect: function(csg) {
var a = new CSG.Node(this.clone().polygons);
var b = new CSG.Node(csg.clone().polygons);
a.invert();
b.clipTo(a);
b.invert();
a.clipTo(b);
b.clipTo(a);
a.build(b.allPolygons());
a.invert();
return CSG.fromPolygons(a.allPolygons());
},
// Return a new CSG solid with solid and empty space switched. This solid is
// not modified.
inverse: function() {
var csg = this.clone();
csg.polygons.map(function(p) { p.flip(); });
return csg;
}
};
// Construct an axis-aligned solid cuboid. Optional parameters are `center` and
// `radius`, which default to `[0, 0, 0]` and `[1, 1, 1]`. The radius can be
// specified using a single number or a list of three numbers, one for each axis.
//
// Example code:
//
// var cube = CSG.cube({
// center: [0, 0, 0],
// radius: 1
// });
CSG.cube = function(options) {
options = options || {};
var c = new CSG.Vector(options.center || [0, 0, 0]);
var r = !options.radius ? [1, 1, 1] : options.radius.length ?
options.radius : [options.radius, options.radius, options.radius];
return CSG.fromPolygons([
[[0, 4, 6, 2], [-1, 0, 0]],
[[1, 3, 7, 5], [+1, 0, 0]],
[[0, 1, 5, 4], [0, -1, 0]],
[[2, 6, 7, 3], [0, +1, 0]],
[[0, 2, 3, 1], [0, 0, -1]],
[[4, 5, 7, 6], [0, 0, +1]]
].map(function(info) {
return new CSG.Polygon(info[0].map(function(i) {
var pos = new CSG.Vector(
c.x + r[0] * (2 * !!(i & 1) - 1),
c.y + r[1] * (2 * !!(i & 2) - 1),
c.z + r[2] * (2 * !!(i & 4) - 1)
);
return new CSG.Vertex(pos, new CSG.Vector(info[1]));
}));
}));
};
// Construct a solid sphere. Optional parameters are `center`, `radius`,
// `slices`, and `stacks`, which default to `[0, 0, 0]`, `1`, `16`, and `8`.
// The `slices` and `stacks` parameters control the tessellation along the
// longitude and latitude directions.
//
// Example usage:
//
// var sphere = CSG.sphere({
// center: [0, 0, 0],
// radius: 1,
// slices: 16,
// stacks: 8
// });
CSG.sphere = function(options) {
options = options || {};
var c = new CSG.Vector(options.center || [0, 0, 0]);
var r = options.radius || 1;
var slices = options.slices || 16;
var stacks = options.stacks || 8;
var polygons = [], vertices;
function vertex(theta, phi) {
theta *= Math.PI * 2;
phi *= Math.PI;
var dir = new CSG.Vector(
Math.cos(theta) * Math.sin(phi),
Math.cos(phi),
Math.sin(theta) * Math.sin(phi)
);
vertices.push(new CSG.Vertex(c.plus(dir.times(r)), dir));
}
for (var i = 0; i < slices; i++) {
for (var j = 0; j < stacks; j++) {
vertices = [];
vertex(i / slices, j / stacks);
if (j > 0) vertex((i + 1) / slices, j / stacks);
if (j < stacks - 1) vertex((i + 1) / slices, (j + 1) / stacks);
vertex(i / slices, (j + 1) / stacks);
polygons.push(new CSG.Polygon(vertices));
}
}
return CSG.fromPolygons(polygons);
};
// Construct a solid cylinder. Optional parameters are `start`, `end`,
// `radius`, and `slices`, which default to `[0, -1, 0]`, `[0, 1, 0]`, `1`, and
// `16`. The `slices` parameter controls the tessellation.
//
// Example usage:
//
// var cylinder = CSG.cylinder({
// start: [0, -1, 0],
// end: [0, 1, 0],
// radius: 1,
// slices: 16
// });
CSG.cylinder = function(options) {
options = options || {};
var s = new CSG.Vector(options.start || [0, -1, 0]);
var e = new CSG.Vector(options.end || [0, 1, 0]);
var ray = e.minus(s);
var r = options.radius || 1;
var slices = options.slices || 16;
var axisZ = ray.unit(), isY = (Math.abs(axisZ.y) > 0.5);
var axisX = new CSG.Vector(isY, !isY, 0).cross(axisZ).unit();
var axisY = axisX.cross(axisZ).unit();
var start = new CSG.Vertex(s, axisZ.negated());
var end = new CSG.Vertex(e, axisZ.unit());
var polygons = [];
function point(stack, slice, normalBlend) {
var angle = slice * Math.PI * 2;
var out = axisX.times(Math.cos(angle)).plus(axisY.times(Math.sin(angle)));
var pos = s.plus(ray.times(stack)).plus(out.times(r));
var normal = out.times(1 - Math.abs(normalBlend)).plus(axisZ.times(normalBlend));
return new CSG.Vertex(pos, normal);
}
for (var i = 0; i < slices; i++) {
var t0 = i / slices, t1 = (i + 1) / slices;
polygons.push(new CSG.Polygon([start, point(0, t0, -1), point(0, t1, -1)]));
polygons.push(new CSG.Polygon([point(0, t1, 0), point(0, t0, 0), point(1, t0, 0), point(1, t1, 0)]));
polygons.push(new CSG.Polygon([end, point(1, t1, 1), point(1, t0, 1)]));
}
return CSG.fromPolygons(polygons);
};
// # class Vector
// Represents a 3D vector.
//
// Example usage:
//
// new CSG.Vector(1, 2, 3);
// new CSG.Vector([1, 2, 3]);
// new CSG.Vector({ x: 1, y: 2, z: 3 });
CSG.Vector = function(x, y, z) {
if (arguments.length == 3) {
this.x = x;
this.y = y;
this.z = z;
} else if ('x' in x) {
this.x = x.x;
this.y = x.y;
this.z = x.z;
} else {
this.x = x[0];
this.y = x[1];
this.z = x[2];
}
};
CSG.Vector.prototype = {
clone: function() {
return new CSG.Vector(this.x, this.y, this.z);
},
negated: function() {
return new CSG.Vector(-this.x, -this.y, -this.z);
},
plus: function(a) {
return new CSG.Vector(this.x + a.x, this.y + a.y, this.z + a.z);
},
minus: function(a) {
return new CSG.Vector(this.x - a.x, this.y - a.y, this.z - a.z);
},
times: function(a) {
return new CSG.Vector(this.x * a, this.y * a, this.z * a);
},
dividedBy: function(a) {
return new CSG.Vector(this.x / a, this.y / a, this.z / a);
},
dot: function(a) {
return this.x * a.x + this.y * a.y + this.z * a.z;
},
lerp: function(a, t) {
return this.plus(a.minus(this).times(t));
},
length: function() {
return Math.sqrt(this.dot(this));
},
unit: function() {
return this.dividedBy(this.length());
},
cross: function(a) {
return new CSG.Vector(
this.y * a.z - this.z * a.y,
this.z * a.x - this.x * a.z,
this.x * a.y - this.y * a.x
);
}
};
// # class Vertex
// Represents a vertex of a polygon. Use your own vertex class instead of this
// one to provide additional features like texture coordinates and vertex
// colors. Custom vertex classes need to provide a `pos` property and `clone()`,
// `flip()`, and `interpolate()` methods that behave analogous to the ones
// defined by `CSG.Vertex`. This class provides `normal` so convenience
// functions like `CSG.sphere()` can return a smooth vertex normal, but `normal`
// is not used anywhere else.
CSG.Vertex = function(pos, normal) {
this.pos = new CSG.Vector(pos);
this.normal = new CSG.Vector(normal);
};
CSG.Vertex.prototype = {
clone: function() {
return new CSG.Vertex(this.pos.clone(), this.normal.clone());
},
// Invert all orientation-specific data (e.g. vertex normal). Called when the
// orientation of a polygon is flipped.
flip: function() {
this.normal = this.normal.negated();
},
// Create a new vertex between this vertex and `other` by linearly
// interpolating all properties using a parameter of `t`. Subclasses should
// override this to interpolate additional properties.
interpolate: function(other, t) {
return new CSG.Vertex(
this.pos.lerp(other.pos, t),
this.normal.lerp(other.normal, t)
);
}
};
// # class Plane
// Represents a plane in 3D space.
CSG.Plane = function(normal, w) {
this.normal = normal;
this.w = w;
};
// `CSG.Plane.EPSILON` is the tolerance used by `splitPolygon()` to decide if a
// point is on the plane.
CSG.Plane.EPSILON = 1e-5;
CSG.Plane.fromPoints = function(a, b, c) {
var n = b.minus(a).cross(c.minus(a)).unit();
return new CSG.Plane(n, n.dot(a));
};
CSG.Plane.prototype = {
clone: function() {
return new CSG.Plane(this.normal.clone(), this.w);
},
flip: function() {
this.normal = this.normal.negated();
this.w = -this.w;
},
// Split `polygon` by this plane if needed, then put the polygon or polygon
// fragments in the appropriate lists. Coplanar polygons go into either
// `coplanarFront` or `coplanarBack` depending on their orientation with
// respect to this plane. Polygons in front or in back of this plane go into
// either `front` or `back`.
splitPolygon: function(polygon, coplanarFront, coplanarBack, front, back) {
var COPLANAR = 0;
var FRONT = 1;
var BACK = 2;
var SPANNING = 3;
// Classify each point as well as the entire polygon into one of the above
// four classes.
var polygonType = 0;
var types = [];
for (var i = 0; i < polygon.vertices.length; i++) {
var t = this.normal.dot(polygon.vertices[i].pos) - this.w;
var type = (t < -CSG.Plane.EPSILON) ? BACK : (t > CSG.Plane.EPSILON) ? FRONT : COPLANAR;
polygonType |= type;
types.push(type);
}
// Put the polygon in the correct list, splitting it when necessary.
switch (polygonType) {
case COPLANAR:
(this.normal.dot(polygon.plane.normal) > 0 ? coplanarFront : coplanarBack).push(polygon);
break;
case FRONT:
front.push(polygon);
break;
case BACK:
back.push(polygon);
break;
case SPANNING:
var f = [], b = [];
for (var i = 0; i < polygon.vertices.length; i++) {
var j = (i + 1) % polygon.vertices.length;
var ti = types[i], tj = types[j];
var vi = polygon.vertices[i], vj = polygon.vertices[j];
if (ti != BACK) f.push(vi);
if (ti != FRONT) b.push(ti != BACK ? vi.clone() : vi);
if ((ti | tj) == SPANNING) {
var t = (this.w - this.normal.dot(vi.pos)) / this.normal.dot(vj.pos.minus(vi.pos));
var v = vi.interpolate(vj, t);
f.push(v);
b.push(v.clone());
}
}
if (f.length >= 3) front.push(new CSG.Polygon(f, polygon.shared));
if (b.length >= 3) back.push(new CSG.Polygon(b, polygon.shared));
break;
}
}
};
// # class Polygon
// Represents a convex polygon. The vertices used to initialize a polygon must
// be coplanar and form a convex loop. They do not have to be `CSG.Vertex`
// instances but they must behave similarly (duck typing can be used for
// customization).
//
// Each convex polygon has a `shared` property, which is shared between all
// polygons that are clones of each other or were split from the same polygon.
// This can be used to define per-polygon properties (such as surface color).
CSG.Polygon = function(vertices, shared) {
this.vertices = vertices;
this.shared = shared;
this.plane = CSG.Plane.fromPoints(vertices[0].pos, vertices[1].pos, vertices[2].pos);
};
CSG.Polygon.prototype = {
clone: function() {
var vertices = this.vertices.map(function(v) { return v.clone(); });
return new CSG.Polygon(vertices, this.shared);
},
flip: function() {
this.vertices.reverse().map(function(v) { v.flip(); });
this.plane.flip();
}
};
// # class Node
// Holds a node in a BSP tree. A BSP tree is built from a collection of polygons
// by picking a polygon to split along. That polygon (and all other coplanar
// polygons) are added directly to that node and the other polygons are added to
// the front and/or back subtrees. This is not a leafy BSP tree since there is
// no distinction between internal and leaf nodes.
CSG.Node = function(polygons) {
this.plane = null;
this.front = null;
this.back = null;
this.polygons = [];
if (polygons) this.build(polygons);
};
CSG.Node.prototype = {
clone: function() {
var node = new CSG.Node();
node.plane = this.plane && this.plane.clone();
node.front = this.front && this.front.clone();
node.back = this.back && this.back.clone();
node.polygons = this.polygons.map(function(p) { return p.clone(); });
return node;
},
// Convert solid space to empty space and empty space to solid space.
invert: function() {
for (var i = 0; i < this.polygons.length; i++) {
this.polygons[i].flip();
}
this.plane.flip();
if (this.front) this.front.invert();
if (this.back) this.back.invert();
var temp = this.front;
this.front = this.back;
this.back = temp;
},
// Recursively remove all polygons in `polygons` that are inside this BSP
// tree.
clipPolygons: function(polygons) {
if (!this.plane) return polygons.slice();
var front = [], back = [];
for (var i = 0; i < polygons.length; i++) {
this.plane.splitPolygon(polygons[i], front, back, front, back);
}
if (this.front) front = this.front.clipPolygons(front);
if (this.back) back = this.back.clipPolygons(back);
else back = [];
return front.concat(back);
},
// Remove all polygons in this BSP tree that are inside the other BSP tree
// `bsp`.
clipTo: function(bsp) {
this.polygons = bsp.clipPolygons(this.polygons);
if (this.front) this.front.clipTo(bsp);
if (this.back) this.back.clipTo(bsp);
},
// Return a list of all polygons in this BSP tree.
allPolygons: function() {
var polygons = this.polygons.slice();
if (this.front) polygons = polygons.concat(this.front.allPolygons());
if (this.back) polygons = polygons.concat(this.back.allPolygons());
return polygons;
},
// Build a BSP tree out of `polygons`. When called on an existing tree, the
// new polygons are filtered down to the bottom of the tree and become new
// nodes there. Each set of polygons is partitioned using the first polygon
// (no heuristic is used to pick a good split).
build: function(polygons) {
if (!polygons.length) return;
if (!this.plane) this.plane = polygons[0].plane.clone();
var front = [], back = [];
for (var i = 0; i < polygons.length; i++) {
this.plane.splitPolygon(polygons[i], this.polygons, this.polygons, front, back);
}
if (front.length) {
if (!this.front) this.front = new CSG.Node();
this.front.build(front);
}
if (back.length) {
if (!this.back) this.back = new CSG.Node();
this.back.build(back);
}
}
};