three.js/src/extras/ShapeUtils.js

/**
 * @author zz85 / http://www.lab4games.net/zz85/blog
 */

var ShapeUtils = {

	// calculate area of the contour polygon

	area: function ( contour ) {

		var n = contour.length;
		var a = 0.0;

		for ( var p = n - 1, q = 0; q < n; p = q ++ ) {

			a += contour[ p ].x * contour[ q ].y - contour[ q ].x * contour[ p ].y;

		}

		return a * 0.5;

	},

	triangulate: ( function () {

		/**
		 * This code is a quick port of code written in C++ which was submitted to
		 * flipcode.com by John W. Ratcliff  // July 22, 2000
		 * See original code and more information here:
		 * http://www.flipcode.com/archives/Efficient_Polygon_Triangulation.shtml
		 *
		 * ported to actionscript by Zevan Rosser
		 * www.actionsnippet.com
		 *
		 * ported to javascript by Joshua Koo
		 * http://www.lab4games.net/zz85/blog
		 *
		 */

		function snip( contour, u, v, w, n, verts ) {

			var p;
			var ax, ay, bx, by;
			var cx, cy, px, py;

			ax = contour[ verts[ u ] ].x;
			ay = contour[ verts[ u ] ].y;

			bx = contour[ verts[ v ] ].x;
			by = contour[ verts[ v ] ].y;

			cx = contour[ verts[ w ] ].x;
			cy = contour[ verts[ w ] ].y;

			if ( ( bx - ax ) * ( cy - ay ) - ( by - ay ) * ( cx - ax ) <= 0 ) return false;

			var aX, aY, bX, bY, cX, cY;
			var apx, apy, bpx, bpy, cpx, cpy;
			var cCROSSap, bCROSScp, aCROSSbp;

			aX = cx - bx; aY = cy - by;
			bX = ax - cx; bY = ay - cy;
			cX = bx - ax; cY = by - ay;

			for ( p = 0; p < n; p ++ ) {

				px = contour[ verts[ p ] ].x;
				py = contour[ verts[ p ] ].y;

				if ( ( ( px === ax ) && ( py === ay ) ) ||
					 ( ( px === bx ) && ( py === by ) ) ||
					 ( ( px === cx ) && ( py === cy ) ) )	continue;

				apx = px - ax; apy = py - ay;
				bpx = px - bx; bpy = py - by;
				cpx = px - cx; cpy = py - cy;

				// see if p is inside triangle abc

				aCROSSbp = aX * bpy - aY * bpx;
				cCROSSap = cX * apy - cY * apx;
				bCROSScp = bX * cpy - bY * cpx;

				if ( ( aCROSSbp >= - Number.EPSILON ) && ( bCROSScp >= - Number.EPSILON ) && ( cCROSSap >= - Number.EPSILON ) ) return false;

			}

			return true;

		}

		// takes in an contour array and returns

		return function triangulate( contour, indices ) {

			var n = contour.length;

			if ( n < 3 ) return null;

			var result = [],
				verts = [],
				vertIndices = [];

			/* we want a counter-clockwise polygon in verts */

			var u, v, w;

			if ( ShapeUtils.area( contour ) > 0.0 ) {

				for ( v = 0; v < n; v ++ ) verts[ v ] = v;

			} else {

				for ( v = 0; v < n; v ++ ) verts[ v ] = ( n - 1 ) - v;

			}

			var nv = n;

			/*  remove nv - 2 vertices, creating 1 triangle every time */

			var count = 2 * nv; /* error detection */

			for ( v = nv - 1; nv > 2; ) {

				/* if we loop, it is probably a non-simple polygon */

				if ( ( count -- ) <= 0 ) {

					//** Triangulate: ERROR - probable bad polygon!

					//throw ( "Warning, unable to triangulate polygon!" );
					//return null;
					// Sometimes warning is fine, especially polygons are triangulated in reverse.
					console.warn( 'THREE.ShapeUtils: Unable to triangulate polygon! in triangulate()' );

					if ( indices ) return vertIndices;
					return result;

				}

				/* three consecutive vertices in current polygon, <u,v,w> */

				u = v; if ( nv <= u ) u = 0; /* previous */
				v = u + 1; if ( nv <= v ) v = 0; /* new v    */
				w = v + 1; if ( nv <= w ) w = 0; /* next     */

				if ( snip( contour, u, v, w, nv, verts ) ) {

					var a, b, c, s, t;

					/* true names of the vertices */

					a = verts[ u ];
					b = verts[ v ];
					c = verts[ w ];

					/* output Triangle */

					result.push( [ contour[ a ],
						contour[ b ],
						contour[ c ] ] );


					vertIndices.push( [ verts[ u ], verts[ v ], verts[ w ] ] );

					/* remove v from the remaining polygon */

					for ( s = v, t = v + 1; t < nv; s ++, t ++ ) {

						verts[ s ] = verts[ t ];

					}

					nv --;

					/* reset error detection counter */

					count = 2 * nv;

				}

			}

			if ( indices ) return vertIndices;
			return result;

		};

	} )(),

	triangulateShape: function ( contour, holes ) {

		function removeDupEndPts( points ) {

			var l = points.length;

			if ( l > 2 && points[ l - 1 ].equals( points[ 0 ] ) ) {

				points.pop();

			}

		}

		removeDupEndPts( contour );
		holes.forEach( removeDupEndPts );

		function point_in_segment_2D_colin( inSegPt1, inSegPt2, inOtherPt ) {

			// inOtherPt needs to be collinear to the inSegment
			if ( inSegPt1.x !== inSegPt2.x ) {

				if ( inSegPt1.x < inSegPt2.x ) {

					return	( ( inSegPt1.x <= inOtherPt.x ) && ( inOtherPt.x <= inSegPt2.x ) );

				} else {

					return	( ( inSegPt2.x <= inOtherPt.x ) && ( inOtherPt.x <= inSegPt1.x ) );

				}

			} else {

				if ( inSegPt1.y < inSegPt2.y ) {

					return	( ( inSegPt1.y <= inOtherPt.y ) && ( inOtherPt.y <= inSegPt2.y ) );

				} else {

					return	( ( inSegPt2.y <= inOtherPt.y ) && ( inOtherPt.y <= inSegPt1.y ) );

				}

			}

		}

		function intersect_segments_2D( inSeg1Pt1, inSeg1Pt2, inSeg2Pt1, inSeg2Pt2, inExcludeAdjacentSegs ) {

			var seg1dx = inSeg1Pt2.x - inSeg1Pt1.x, seg1dy = inSeg1Pt2.y - inSeg1Pt1.y;
			var seg2dx = inSeg2Pt2.x - inSeg2Pt1.x, seg2dy = inSeg2Pt2.y - inSeg2Pt1.y;

			var seg1seg2dx = inSeg1Pt1.x - inSeg2Pt1.x;
			var seg1seg2dy = inSeg1Pt1.y - inSeg2Pt1.y;

			var limit		= seg1dy * seg2dx - seg1dx * seg2dy;
			var perpSeg1	= seg1dy * seg1seg2dx - seg1dx * seg1seg2dy;

			if ( Math.abs( limit ) > Number.EPSILON ) {

				// not parallel

				var perpSeg2;
				if ( limit > 0 ) {

					if ( ( perpSeg1 < 0 ) || ( perpSeg1 > limit ) ) 		return [];
					perpSeg2 = seg2dy * seg1seg2dx - seg2dx * seg1seg2dy;
					if ( ( perpSeg2 < 0 ) || ( perpSeg2 > limit ) ) 		return [];

				} else {

					if ( ( perpSeg1 > 0 ) || ( perpSeg1 < limit ) ) 		return [];
					perpSeg2 = seg2dy * seg1seg2dx - seg2dx * seg1seg2dy;
					if ( ( perpSeg2 > 0 ) || ( perpSeg2 < limit ) ) 		return [];

				}

				// i.e. to reduce rounding errors
				// intersection at endpoint of segment#1?
				if ( perpSeg2 === 0 ) {

					if ( ( inExcludeAdjacentSegs ) &&
						 ( ( perpSeg1 === 0 ) || ( perpSeg1 === limit ) ) )		return [];
					return [ inSeg1Pt1 ];

				}
				if ( perpSeg2 === limit ) {

					if ( ( inExcludeAdjacentSegs ) &&
						 ( ( perpSeg1 === 0 ) || ( perpSeg1 === limit ) ) )		return [];
					return [ inSeg1Pt2 ];

				}
				// intersection at endpoint of segment#2?
				if ( perpSeg1 === 0 )		return [ inSeg2Pt1 ];
				if ( perpSeg1 === limit )	return [ inSeg2Pt2 ];

				// return real intersection point
				var factorSeg1 = perpSeg2 / limit;
				return	[ { x: inSeg1Pt1.x + factorSeg1 * seg1dx, y: inSeg1Pt1.y + factorSeg1 * seg1dy } ];

			} else {

				// parallel or collinear
				if ( ( perpSeg1 !== 0 ) ||
					 ( seg2dy * seg1seg2dx !== seg2dx * seg1seg2dy ) ) 			return [];

				// they are collinear or degenerate
				var seg1Pt = ( ( seg1dx === 0 ) && ( seg1dy === 0 ) );	// segment1 is just a point?
				var seg2Pt = ( ( seg2dx === 0 ) && ( seg2dy === 0 ) );	// segment2 is just a point?
				// both segments are points
				if ( seg1Pt && seg2Pt ) {

					if ( ( inSeg1Pt1.x !== inSeg2Pt1.x ) ||
						 ( inSeg1Pt1.y !== inSeg2Pt1.y ) )		return [];	// they are distinct  points
					return [ inSeg1Pt1 ];	// they are the same point

				}
				// segment#1  is a single point
				if ( seg1Pt ) {

					if ( ! point_in_segment_2D_colin( inSeg2Pt1, inSeg2Pt2, inSeg1Pt1 ) )		return [];		// but not in segment#2
					return [ inSeg1Pt1 ];

				}
				// segment#2  is a single point
				if ( seg2Pt ) {

					if ( ! point_in_segment_2D_colin( inSeg1Pt1, inSeg1Pt2, inSeg2Pt1 ) )		return [];		// but not in segment#1
					return [ inSeg2Pt1 ];

				}

				// they are collinear segments, which might overlap
				var seg1min, seg1max, seg1minVal, seg1maxVal;
				var seg2min, seg2max, seg2minVal, seg2maxVal;
				if ( seg1dx !== 0 ) {

					// the segments are NOT on a vertical line
					if ( inSeg1Pt1.x < inSeg1Pt2.x ) {

						seg1min = inSeg1Pt1; seg1minVal = inSeg1Pt1.x;
						seg1max = inSeg1Pt2; seg1maxVal = inSeg1Pt2.x;

					} else {

						seg1min = inSeg1Pt2; seg1minVal = inSeg1Pt2.x;
						seg1max = inSeg1Pt1; seg1maxVal = inSeg1Pt1.x;

					}
					if ( inSeg2Pt1.x < inSeg2Pt2.x ) {

						seg2min = inSeg2Pt1; seg2minVal = inSeg2Pt1.x;
						seg2max = inSeg2Pt2; seg2maxVal = inSeg2Pt2.x;

					} else {

						seg2min = inSeg2Pt2; seg2minVal = inSeg2Pt2.x;
						seg2max = inSeg2Pt1; seg2maxVal = inSeg2Pt1.x;

					}

				} else {

					// the segments are on a vertical line
					if ( inSeg1Pt1.y < inSeg1Pt2.y ) {

						seg1min = inSeg1Pt1; seg1minVal = inSeg1Pt1.y;
						seg1max = inSeg1Pt2; seg1maxVal = inSeg1Pt2.y;

					} else {

						seg1min = inSeg1Pt2; seg1minVal = inSeg1Pt2.y;
						seg1max = inSeg1Pt1; seg1maxVal = inSeg1Pt1.y;

					}
					if ( inSeg2Pt1.y < inSeg2Pt2.y ) {

						seg2min = inSeg2Pt1; seg2minVal = inSeg2Pt1.y;
						seg2max = inSeg2Pt2; seg2maxVal = inSeg2Pt2.y;

					} else {

						seg2min = inSeg2Pt2; seg2minVal = inSeg2Pt2.y;
						seg2max = inSeg2Pt1; seg2maxVal = inSeg2Pt1.y;

					}

				}
				if ( seg1minVal <= seg2minVal ) {

					if ( seg1maxVal < seg2minVal )	return [];
					if ( seg1maxVal === seg2minVal )	{

						if ( inExcludeAdjacentSegs )		return [];
						return [ seg2min ];

					}
					if ( seg1maxVal <= seg2maxVal )	return [ seg2min, seg1max ];
					return	[ seg2min, seg2max ];

				} else {

					if ( seg1minVal > seg2maxVal )	return [];
					if ( seg1minVal === seg2maxVal )	{

						if ( inExcludeAdjacentSegs )		return [];
						return [ seg1min ];

					}
					if ( seg1maxVal <= seg2maxVal )	return [ seg1min, seg1max ];
					return	[ seg1min, seg2max ];

				}

			}

		}

		function isPointInsideAngle( inVertex, inLegFromPt, inLegToPt, inOtherPt ) {

			// The order of legs is important

			// translation of all points, so that Vertex is at (0,0)
			var legFromPtX	= inLegFromPt.x - inVertex.x, legFromPtY = inLegFromPt.y - inVertex.y;
			var legToPtX	= inLegToPt.x	- inVertex.x, legToPtY = inLegToPt.y	- inVertex.y;
			var otherPtX	= inOtherPt.x	- inVertex.x, otherPtY = inOtherPt.y	- inVertex.y;

			// main angle >0: < 180 deg.; 0: 180 deg.; <0: > 180 deg.
			var from2toAngle	= legFromPtX * legToPtY - legFromPtY * legToPtX;
			var from2otherAngle	= legFromPtX * otherPtY - legFromPtY * otherPtX;

			if ( Math.abs( from2toAngle ) > Number.EPSILON ) {

				// angle != 180 deg.

				var other2toAngle		= otherPtX * legToPtY - otherPtY * legToPtX;
				// console.log( "from2to: " + from2toAngle + ", from2other: " + from2otherAngle + ", other2to: " + other2toAngle );

				if ( from2toAngle > 0 ) {

					// main angle < 180 deg.
					return	( ( from2otherAngle >= 0 ) && ( other2toAngle >= 0 ) );

				} else {

					// main angle > 180 deg.
					return	( ( from2otherAngle >= 0 ) || ( other2toAngle >= 0 ) );

				}

			} else {

				// angle == 180 deg.
				// console.log( "from2to: 180 deg., from2other: " + from2otherAngle  );
				return	( from2otherAngle > 0 );

			}

		}


		function removeHoles( contour, holes ) {

			var shape = contour.concat(); // work on this shape
			var hole;

			function isCutLineInsideAngles( inShapeIdx, inHoleIdx ) {

				// Check if hole point lies within angle around shape point
				var lastShapeIdx = shape.length - 1;

				var prevShapeIdx = inShapeIdx - 1;
				if ( prevShapeIdx < 0 )			prevShapeIdx = lastShapeIdx;

				var nextShapeIdx = inShapeIdx + 1;
				if ( nextShapeIdx > lastShapeIdx )	nextShapeIdx = 0;

				var insideAngle = isPointInsideAngle( shape[ inShapeIdx ], shape[ prevShapeIdx ], shape[ nextShapeIdx ], hole[ inHoleIdx ] );
				if ( ! insideAngle ) {

					// console.log( "Vertex (Shape): " + inShapeIdx + ", Point: " + hole[inHoleIdx].x + "/" + hole[inHoleIdx].y );
					return	false;

				}

				// Check if shape point lies within angle around hole point
				var lastHoleIdx = hole.length - 1;

				var prevHoleIdx = inHoleIdx - 1;
				if ( prevHoleIdx < 0 )			prevHoleIdx = lastHoleIdx;

				var nextHoleIdx = inHoleIdx + 1;
				if ( nextHoleIdx > lastHoleIdx )	nextHoleIdx = 0;

				insideAngle = isPointInsideAngle( hole[ inHoleIdx ], hole[ prevHoleIdx ], hole[ nextHoleIdx ], shape[ inShapeIdx ] );
				if ( ! insideAngle ) {

					// console.log( "Vertex (Hole): " + inHoleIdx + ", Point: " + shape[inShapeIdx].x + "/" + shape[inShapeIdx].y );
					return	false;

				}

				return	true;

			}

			function intersectsShapeEdge( inShapePt, inHolePt ) {

				// checks for intersections with shape edges
				var sIdx, nextIdx, intersection;
				for ( sIdx = 0; sIdx < shape.length; sIdx ++ ) {

					nextIdx = sIdx + 1; nextIdx %= shape.length;
					intersection = intersect_segments_2D( inShapePt, inHolePt, shape[ sIdx ], shape[ nextIdx ], true );
					if ( intersection.length > 0 )		return	true;

				}

				return	false;

			}

			var indepHoles = [];

			function intersectsHoleEdge( inShapePt, inHolePt ) {

				// checks for intersections with hole edges
				var ihIdx, chkHole,
					hIdx, nextIdx, intersection;
				for ( ihIdx = 0; ihIdx < indepHoles.length; ihIdx ++ ) {

					chkHole = holes[ indepHoles[ ihIdx ] ];
					for ( hIdx = 0; hIdx < chkHole.length; hIdx ++ ) {

						nextIdx = hIdx + 1; nextIdx %= chkHole.length;
						intersection = intersect_segments_2D( inShapePt, inHolePt, chkHole[ hIdx ], chkHole[ nextIdx ], true );
						if ( intersection.length > 0 )		return	true;

					}

				}
				return	false;

			}

			var holeIndex, shapeIndex,
				shapePt, holePt,
				holeIdx, cutKey, failedCuts = [],
				tmpShape1, tmpShape2,
				tmpHole1, tmpHole2;

			for ( var h = 0, hl = holes.length; h < hl; h ++ ) {

				indepHoles.push( h );

			}

			var minShapeIndex = 0;
			var counter = indepHoles.length * 2;
			while ( indepHoles.length > 0 ) {

				counter --;
				if ( counter < 0 ) {

					console.log( 'THREE.ShapeUtils: Infinite Loop! Holes left:" + indepHoles.length + ", Probably Hole outside Shape!' );
					break;

				}

				// search for shape-vertex and hole-vertex,
				// which can be connected without intersections
				for ( shapeIndex = minShapeIndex; shapeIndex < shape.length; shapeIndex ++ ) {

					shapePt = shape[ shapeIndex ];
					holeIndex	= - 1;

					// search for hole which can be reached without intersections
					for ( var h = 0; h < indepHoles.length; h ++ ) {

						holeIdx = indepHoles[ h ];

						// prevent multiple checks
						cutKey = shapePt.x + ':' + shapePt.y + ':' + holeIdx;
						if ( failedCuts[ cutKey ] !== undefined )			continue;

						hole = holes[ holeIdx ];
						for ( var h2 = 0; h2 < hole.length; h2 ++ ) {

							holePt = hole[ h2 ];
							if ( ! isCutLineInsideAngles( shapeIndex, h2 ) )		continue;
							if ( intersectsShapeEdge( shapePt, holePt ) )		continue;
							if ( intersectsHoleEdge( shapePt, holePt ) )		continue;

							holeIndex = h2;
							indepHoles.splice( h, 1 );

							tmpShape1 = shape.slice( 0, shapeIndex + 1 );
							tmpShape2 = shape.slice( shapeIndex );
							tmpHole1 = hole.slice( holeIndex );
							tmpHole2 = hole.slice( 0, holeIndex + 1 );

							shape = tmpShape1.concat( tmpHole1 ).concat( tmpHole2 ).concat( tmpShape2 );

							minShapeIndex = shapeIndex;

							// Debug only, to show the selected cuts
							// glob_CutLines.push( [ shapePt, holePt ] );

							break;

						}
						if ( holeIndex >= 0 )	break;		// hole-vertex found

						failedCuts[ cutKey ] = true;			// remember failure

					}
					if ( holeIndex >= 0 )	break;		// hole-vertex found

				}

			}

			return shape; 			/* shape with no holes */

		}


		var i, il, f, face,
			key, index,
			allPointsMap = {};

		// To maintain reference to old shape, one must match coordinates, or offset the indices from original arrays. It's probably easier to do the first.

		var allpoints = contour.concat();

		for ( var h = 0, hl = holes.length; h < hl; h ++ ) {

			Array.prototype.push.apply( allpoints, holes[ h ] );

		}

		//console.log( "allpoints",allpoints, allpoints.length );

		// prepare all points map

		for ( i = 0, il = allpoints.length; i < il; i ++ ) {

			key = allpoints[ i ].x + ':' + allpoints[ i ].y;

			if ( allPointsMap[ key ] !== undefined ) {

				console.warn( 'THREE.ShapeUtils: Duplicate point', key, i );

			}

			allPointsMap[ key ] = i;

		}

		// remove holes by cutting paths to holes and adding them to the shape
		var shapeWithoutHoles = removeHoles( contour, holes );

		var triangles = ShapeUtils.triangulate( shapeWithoutHoles, false ); // True returns indices for points of spooled shape
		//console.log( "triangles",triangles, triangles.length );

		// check all face vertices against all points map

		for ( i = 0, il = triangles.length; i < il; i ++ ) {

			face = triangles[ i ];

			for ( f = 0; f < 3; f ++ ) {

				key = face[ f ].x + ':' + face[ f ].y;

				index = allPointsMap[ key ];

				if ( index !== undefined ) {

					face[ f ] = index;

				}

			}

		}

		return triangles.concat();

	},

	isClockWise: function ( pts ) {

		return ShapeUtils.area( pts ) < 0;

	}

};


export { ShapeUtils };