web-ifc-viewer
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122 lines • 4.26 kB
JavaScript
export class SelectionBoxMath {
// https://www.geeksforgeeks.org/convex-hull-set-2-graham-scan/
getConvexHull(points) {
// find the lowest point in 2d
let lowestY = Infinity;
let lowestIndex = -1;
for (let i = 0, l = points.length; i < l; i++) {
const p = points[i];
if (p.y < lowestY) {
lowestIndex = i;
lowestY = p.y;
}
}
// sort the points
const p0 = points[lowestIndex];
points[lowestIndex] = points[0];
points[0] = p0;
function orientation(p, q, r) {
const val = (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y);
if (val === 0) {
return 0; // colinear
}
// clock or counterclock wise
return val > 0 ? 1 : 2;
}
function distSq(p1, p2) {
return (p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y);
}
function compare(p1, p2) {
// Find orientation
const o = orientation(p0, p1, p2);
if (o === 0)
return distSq(p0, p2) >= distSq(p0, p1) ? -1 : 1;
return o === 2 ? -1 : 1;
}
points = points.sort(compare);
// filter the points
let m = 1;
const n = points.length;
for (let i = 1; i < n; i++) {
while (i < n - 1 && orientation(p0, points[i], points[i + 1]) === 0) {
i++;
}
points[m] = points[i];
m++;
}
// early out if we don't have enough points for a hull
if (m < 3)
return null;
// generate the hull
const hull = [points[0], points[1], points[2]];
for (let i = 3; i < m; i++) {
while (orientation(hull[hull.length - 2], hull[hull.length - 1], points[i]) !== 2) {
hull.pop();
}
hull.push(points[i]);
}
return hull;
}
pointRayCrossesLine(point, line, prevDirection, thisDirection) {
const { start, end } = line;
const px = point.x;
const py = point.y;
const sy = start.y;
const ey = end.y;
if (sy === ey)
return false;
if (py > sy && py > ey)
return false; // above
if (py < sy && py < ey)
return false; // below
const sx = start.x;
const ex = end.x;
if (px > sx && px > ex)
return false; // right
if (px < sx && px < ex) {
// left
if (py === sy && prevDirection !== thisDirection) {
return false;
}
return true;
}
// check the side
const dx = ex - sx;
const dy = ey - sy;
const perpx = dy;
const perpy = -dx;
const pdx = px - sx;
const pdy = py - sy;
const dot = perpx * pdx + perpy * pdy;
if (Math.sign(dot) !== Math.sign(perpx)) {
return true;
}
return false;
}
pointRayCrossesSegments(point, segments) {
let crossings = 0;
const firstSeg = segments[segments.length - 1];
let prevDirection = firstSeg.start.y > firstSeg.end.y;
for (let s = 0, l = segments.length; s < l; s++) {
const line = segments[s];
const thisDirection = line.start.y > line.end.y;
if (this.pointRayCrossesLine(point, line, prevDirection, thisDirection)) {
crossings++;
}
prevDirection = thisDirection;
}
return crossings;
}
// https://stackoverflow.com/questions/3838329/how-can-i-check-if-two-segments-intersect
lineCrossesLine(l1, l2) {
function ccw(A, B, C) {
return (C.y - A.y) * (B.x - A.x) > (B.y - A.y) * (C.x - A.x);
}
const A = l1.start;
const B = l1.end;
const C = l2.start;
const D = l2.end;
return ccw(A, C, D) !== ccw(B, C, D) && ccw(A, B, C) !== ccw(A, B, D);
}
}
//# sourceMappingURL=selection-window-math.js.map