/**
* @author zz85 / http://twitter.com/blurspline / http://www.lab4games.net/zz85/blog
*
* Simplification Geometry Modifier
* - based on code and technique
* - by Stan Melax in 1998
* - Progressive Mesh type Polygon Reduction Algorithm
* - http://www.melax.com/polychop/
*/
import {
BufferGeometry,
Float32BufferAttribute,
Geometry,
Vector3
} from "../../../build/three.module.js";
var SimplifyModifier = function () {};
( function () {
var cb = new Vector3(), ab = new 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 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 );
};
SimplifyModifier.prototype.modify = function ( geometry, count ) {
if ( geometry.isBufferGeometry ) {
geometry = new Geometry().fromBufferGeometry( geometry );
}
geometry.mergeVertices();
var oldVertices = geometry.vertices; // Three Position
var oldFaces = geometry.faces; // Three Face
// conversion
var vertices = [];
var faces = [];
var i, il;
//
// put data of original geometry in different data structures
//
// add vertices
for ( i = 0, il = oldVertices.length; i < il; i ++ ) {
var vertex = new Vertex( oldVertices[ i ], i );
vertices.push( vertex );
}
// add faces
for ( i = 0, il = oldFaces.length; i < il; i ++ ) {
var face = oldFaces[ i ];
var a = face.a;
var b = face.b;
var c = face.c;
var triangle = new Triangle( vertices[ a ], vertices[ b ], vertices[ c ], a, b, c );
faces.push( triangle );
}
// compute all edge collapse costs
for ( 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 BufferGeometry();
var position = [];
var index = [];
//
for ( i = 0; i < vertices.length; i ++ ) {
var vertex = vertices[ i ].position;
position.push( vertex.x, vertex.y, vertex.z );
}
//
for ( 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 Float32BufferAttribute( position, 3 ) );
simplifiedGeometry.setIndex( index );
return simplifiedGeometry;
};
} )();
export { SimplifyModifier };
