https://github.com/WWBN/AVideo/issues/8713

node_modules/three/examples/js/modifiers/SimplifyModifier.js

@@ -0,0 +1,527 @@
+/**
+ *	Simplification Geometry Modifier
+ *    - based on code and technique
+ *	  - by Stan Melax in 1998
+ *	  - Progressive Mesh type Polygon Reduction Algorithm
+ *    - http://www.melax.com/polychop/
+ */
+
+THREE.SimplifyModifier = function () {
+
+	if ( THREE.BufferGeometryUtils === undefined ) {
+
+		throw 'THREE.SimplifyModifier relies on THREE.BufferGeometryUtils';
+
+	}
+
+};
+
+( function () {
+
+	var cb = new THREE.Vector3(), ab = new THREE.Vector3();
+
+	function pushIfUnique( array, object ) {
+
+		if ( array.indexOf( object ) === - 1 ) array.push( object );
+
+	}
+
+	function removeFromArray( array, object ) {
+
+		var k = array.indexOf( object );
+		if ( k > - 1 ) array.splice( k, 1 );
+
+	}
+
+	function computeEdgeCollapseCost( u, v ) {
+
+		// if we collapse edge uv by moving u to v then how
+		// much different will the model change, i.e. the "error".
+
+		var edgelength = v.position.distanceTo( u.position );
+		var curvature = 0;
+
+		var sideFaces = [];
+		var i, il = u.faces.length, face, sideFace;
+
+		// find the "sides" triangles that are on the edge uv
+		for ( i = 0; i < il; i ++ ) {
+
+			face = u.faces[ i ];
+
+			if ( face.hasVertex( v ) ) {
+
+				sideFaces.push( face );
+
+			}
+
+		}
+
+		// use the triangle facing most away from the sides
+		// to determine our curvature term
+		for ( i = 0; i < il; i ++ ) {
+
+			var minCurvature = 1;
+			face = u.faces[ i ];
+
+			for ( var j = 0; j < sideFaces.length; j ++ ) {
+
+				sideFace = sideFaces[ j ];
+				// use dot product of face normals.
+				var dotProd = face.normal.dot( sideFace.normal );
+				minCurvature = Math.min( minCurvature, ( 1.001 - dotProd ) / 2 );
+
+			}
+
+			curvature = Math.max( curvature, minCurvature );
+
+		}
+
+		// crude approach in attempt to preserve borders
+		// though it seems not to be totally correct
+		var borders = 0;
+		if ( sideFaces.length < 2 ) {
+
+			// we add some arbitrary cost for borders,
+			// borders += 10;
+			curvature = 1;
+
+		}
+
+		var amt = edgelength * curvature + borders;
+
+		return amt;
+
+	}
+
+	function computeEdgeCostAtVertex( v ) {
+
+		// compute the edge collapse cost for all edges that start
+		// from vertex v.  Since we are only interested in reducing
+		// the object by selecting the min cost edge at each step, we
+		// only cache the cost of the least cost edge at this vertex
+		// (in member variable collapse) as well as the value of the
+		// cost (in member variable collapseCost).
+
+		if ( v.neighbors.length === 0 ) {
+
+			// collapse if no neighbors.
+			v.collapseNeighbor = null;
+			v.collapseCost = - 0.01;
+
+			return;
+
+		}
+
+		v.collapseCost = 100000;
+		v.collapseNeighbor = null;
+
+		// search all neighboring edges for "least cost" edge
+		for ( var i = 0; i < v.neighbors.length; i ++ ) {
+
+			var collapseCost = computeEdgeCollapseCost( v, v.neighbors[ i ] );
+
+			if ( ! v.collapseNeighbor ) {
+
+				v.collapseNeighbor = v.neighbors[ i ];
+				v.collapseCost = collapseCost;
+				v.minCost = collapseCost;
+				v.totalCost = 0;
+				v.costCount = 0;
+
+			}
+
+			v.costCount ++;
+			v.totalCost += collapseCost;
+
+			if ( collapseCost < v.minCost ) {
+
+				v.collapseNeighbor = v.neighbors[ i ];
+				v.minCost = collapseCost;
+
+			}
+
+		}
+
+		// we average the cost of collapsing at this vertex
+		v.collapseCost = v.totalCost / v.costCount;
+		// v.collapseCost = v.minCost;
+
+	}
+
+	function removeVertex( v, vertices ) {
+
+		console.assert( v.faces.length === 0 );
+
+		while ( v.neighbors.length ) {
+
+			var n = v.neighbors.pop();
+			removeFromArray( n.neighbors, v );
+
+		}
+
+		removeFromArray( vertices, v );
+
+	}
+
+	function removeFace( f, faces ) {
+
+		removeFromArray( faces, f );
+
+		if ( f.v1 ) removeFromArray( f.v1.faces, f );
+		if ( f.v2 ) removeFromArray( f.v2.faces, f );
+		if ( f.v3 ) removeFromArray( f.v3.faces, f );
+
+		// TODO optimize this!
+		var vs = [ f.v1, f.v2, f.v3 ];
+		var v1, v2;
+
+		for ( var i = 0; i < 3; i ++ ) {
+
+			v1 = vs[ i ];
+			v2 = vs[ ( i + 1 ) % 3 ];
+
+			if ( ! v1 || ! v2 ) continue;
+
+			v1.removeIfNonNeighbor( v2 );
+			v2.removeIfNonNeighbor( v1 );
+
+		}
+
+	}
+
+	function collapse( vertices, faces, u, v ) { // u and v are pointers to vertices of an edge
+
+		// Collapse the edge uv by moving vertex u onto v
+
+		if ( ! v ) {
+
+			// u is a vertex all by itself so just delete it..
+			removeVertex( u, vertices );
+			return;
+
+		}
+
+		var i;
+		var tmpVertices = [];
+
+		for ( i = 0; i < u.neighbors.length; i ++ ) {
+
+			tmpVertices.push( u.neighbors[ i ] );
+
+		}
+
+
+		// delete triangles on edge uv:
+		for ( i = u.faces.length - 1; i >= 0; i -- ) {
+
+			if ( u.faces[ i ].hasVertex( v ) ) {
+
+				removeFace( u.faces[ i ], faces );
+
+			}
+
+		}
+
+		// update remaining triangles to have v instead of u
+		for ( i = u.faces.length - 1; i >= 0; i -- ) {
+
+			u.faces[ i ].replaceVertex( u, v );
+
+		}
+
+
+		removeVertex( u, vertices );
+
+		// recompute the edge collapse costs in neighborhood
+		for ( i = 0; i < tmpVertices.length; i ++ ) {
+
+			computeEdgeCostAtVertex( tmpVertices[ i ] );
+
+		}
+
+	}
+
+
+
+	function minimumCostEdge( vertices ) {
+
+		// O(n * n) approach. TODO optimize this
+
+		var least = vertices[ 0 ];
+
+		for ( var i = 0; i < vertices.length; i ++ ) {
+
+			if ( vertices[ i ].collapseCost < least.collapseCost ) {
+
+				least = vertices[ i ];
+
+			}
+
+		}
+
+		return least;
+
+	}
+
+	// we use a triangle class to represent structure of face slightly differently
+
+	function Triangle( v1, v2, v3, a, b, c ) {
+
+		this.a = a;
+		this.b = b;
+		this.c = c;
+
+		this.v1 = v1;
+		this.v2 = v2;
+		this.v3 = v3;
+
+		this.normal = new THREE.Vector3();
+
+		this.computeNormal();
+
+		v1.faces.push( this );
+		v1.addUniqueNeighbor( v2 );
+		v1.addUniqueNeighbor( v3 );
+
+		v2.faces.push( this );
+		v2.addUniqueNeighbor( v1 );
+		v2.addUniqueNeighbor( v3 );
+
+
+		v3.faces.push( this );
+		v3.addUniqueNeighbor( v1 );
+		v3.addUniqueNeighbor( v2 );
+
+	}
+
+	Triangle.prototype.computeNormal = function () {
+
+		var vA = this.v1.position;
+		var vB = this.v2.position;
+		var vC = this.v3.position;
+
+		cb.subVectors( vC, vB );
+		ab.subVectors( vA, vB );
+		cb.cross( ab ).normalize();
+
+		this.normal.copy( cb );
+
+	};
+
+	Triangle.prototype.hasVertex = function ( v ) {
+
+		return v === this.v1 || v === this.v2 || v === this.v3;
+
+	};
+
+	Triangle.prototype.replaceVertex = function ( oldv, newv ) {
+
+		if ( oldv === this.v1 ) this.v1 = newv;
+		else if ( oldv === this.v2 ) this.v2 = newv;
+		else if ( oldv === this.v3 ) this.v3 = newv;
+
+		removeFromArray( oldv.faces, this );
+		newv.faces.push( this );
+
+
+		oldv.removeIfNonNeighbor( this.v1 );
+		this.v1.removeIfNonNeighbor( oldv );
+
+		oldv.removeIfNonNeighbor( this.v2 );
+		this.v2.removeIfNonNeighbor( oldv );
+
+		oldv.removeIfNonNeighbor( this.v3 );
+		this.v3.removeIfNonNeighbor( oldv );
+
+		this.v1.addUniqueNeighbor( this.v2 );
+		this.v1.addUniqueNeighbor( this.v3 );
+
+		this.v2.addUniqueNeighbor( this.v1 );
+		this.v2.addUniqueNeighbor( this.v3 );
+
+		this.v3.addUniqueNeighbor( this.v1 );
+		this.v3.addUniqueNeighbor( this.v2 );
+
+		this.computeNormal();
+
+	};
+
+	function Vertex( v, id ) {
+
+		this.position = v;
+
+		this.id = id; // old index id
+
+		this.faces = []; // faces vertex is connected
+		this.neighbors = []; // neighbouring vertices aka "adjacentVertices"
+
+		// these will be computed in computeEdgeCostAtVertex()
+		this.collapseCost = 0; // cost of collapsing this vertex, the less the better. aka objdist
+		this.collapseNeighbor = null; // best candinate for collapsing
+
+	}
+
+	Vertex.prototype.addUniqueNeighbor = function ( vertex ) {
+
+		pushIfUnique( this.neighbors, vertex );
+
+	};
+
+	Vertex.prototype.removeIfNonNeighbor = function ( n ) {
+
+		var neighbors = this.neighbors;
+		var faces = this.faces;
+
+		var offset = neighbors.indexOf( n );
+		if ( offset === - 1 ) return;
+		for ( var i = 0; i < faces.length; i ++ ) {
+
+			if ( faces[ i ].hasVertex( n ) ) return;
+
+		}
+
+		neighbors.splice( offset, 1 );
+
+	};
+
+	THREE.SimplifyModifier.prototype.modify = function ( geometry, count ) {
+
+		if ( geometry.isGeometry === true ) {
+
+			console.error( 'THREE.SimplifyModifier no longer supports THREE.Geometry. Use THREE.BufferGeometry instead.' );
+			return;
+
+		}
+
+		geometry = geometry.clone();
+		var attributes = geometry.attributes;
+
+		// this modifier can only process indexed and non-indexed geomtries with a position attribute
+
+		for ( var name in attributes ) {
+
+			if ( name !== 'position' ) geometry.deleteAttribute( name );
+
+		}
+
+		geometry = THREE.BufferGeometryUtils.mergeVertices( geometry );
+
+		//
+		// put data of original geometry in different data structures
+		//
+
+		var vertices = [];
+		var faces = [];
+
+		// add vertices
+
+		var positionAttribute = geometry.getAttribute( 'position' );
+
+		for ( var i = 0; i < positionAttribute.count; i ++ ) {
+
+			var v = new THREE.Vector3().fromBufferAttribute( positionAttribute, i );
+
+			var vertex = new Vertex( v, i );
+			vertices.push( vertex );
+
+		}
+
+		// add faces
+
+		var index = geometry.getIndex();
+
+		if ( index !== null ) {
+
+			for ( var i = 0; i < index.count; i += 3 ) {
+
+				var a = index.getX( i );
+				var b = index.getX( i + 1 );
+				var c = index.getX( i + 2 );
+
+				var triangle = new Triangle( vertices[ a ], vertices[ b ], vertices[ c ], a, b, c );
+				faces.push( triangle );
+
+			}
+
+		} else {
+
+			for ( var i = 0; i < positionAttribute.count; i += 3 ) {
+
+				var a = i;
+				var b = i + 1;
+				var c = i + 2;
+
+				var triangle = new Triangle( vertices[ a ], vertices[ b ], vertices[ c ], a, b, c );
+				faces.push( triangle );
+
+			}
+
+		}
+
+		// compute all edge collapse costs
+
+		for ( var i = 0, il = vertices.length; i < il; i ++ ) {
+
+			computeEdgeCostAtVertex( vertices[ i ] );
+
+		}
+
+		var nextVertex;
+
+		var z = count;
+
+		while ( z -- ) {
+
+			nextVertex = minimumCostEdge( vertices );
+
+			if ( ! nextVertex ) {
+
+				console.log( 'THREE.SimplifyModifier: No next vertex' );
+				break;
+
+			}
+
+			collapse( vertices, faces, nextVertex, nextVertex.collapseNeighbor );
+
+		}
+
+		//
+
+		var simplifiedGeometry = new THREE.BufferGeometry();
+		var position = [];
+		var index = [];
+
+		//
+
+		for ( var i = 0; i < vertices.length; i ++ ) {
+
+			var vertex = vertices[ i ].position;
+			position.push( vertex.x, vertex.y, vertex.z );
+
+		}
+
+		//
+
+		for ( var i = 0; i < faces.length; i ++ ) {
+
+			var face = faces[ i ];
+
+			var a = vertices.indexOf( face.v1 );
+			var b = vertices.indexOf( face.v2 );
+			var c = vertices.indexOf( face.v3 );
+
+			index.push( a, b, c );
+
+		}
+
+		//
+
+		simplifiedGeometry.setAttribute( 'position', new THREE.Float32BufferAttribute( position, 3 ) );
+		simplifiedGeometry.setIndex( index );
+
+		return simplifiedGeometry;
+
+	};
+
+} )();