ShapeUtils.js•1.52 kB
import { Earcut } from './Earcut.js';
class ShapeUtils {
// calculate area of the contour polygon
static area( contour ) {
const n = contour.length;
let a = 0.0;
for ( let 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;
}
static isClockWise( pts ) {
return ShapeUtils.area( pts ) < 0;
}
static triangulateShape( contour, holes ) {
const vertices = []; // flat array of vertices like [ x0,y0, x1,y1, x2,y2, ... ]
const holeIndices = []; // array of hole indices
const faces = []; // final array of vertex indices like [ [ a,b,d ], [ b,c,d ] ]
removeDupEndPts( contour );
addContour( vertices, contour );
//
let holeIndex = contour.length;
holes.forEach( removeDupEndPts );
for ( let i = 0; i < holes.length; i ++ ) {
holeIndices.push( holeIndex );
holeIndex += holes[ i ].length;
addContour( vertices, holes[ i ] );
}
//
const triangles = Earcut.triangulate( vertices, holeIndices );
//
for ( let i = 0; i < triangles.length; i += 3 ) {
faces.push( triangles.slice( i, i + 3 ) );
}
return faces;
}
}
function removeDupEndPts( points ) {
const l = points.length;
if ( l > 2 && points[ l - 1 ].equals( points[ 0 ] ) ) {
points.pop();
}
}
function addContour( vertices, contour ) {
for ( let i = 0; i < contour.length; i ++ ) {
vertices.push( contour[ i ].x );
vertices.push( contour[ i ].y );
}
}
export { ShapeUtils };