import { mat2, vec2 } from 'gl-matrix'; import { Collidable } from './collision'; const rot90 = mat2.fromValues( 0, 1, -1, 0, ); export function normal(out: vec2, a: vec2): vec2 { return vec2.transformMat2(out, a, rot90); } export function crossz(a: vec2, b: vec2): number { return a[0] * b[1] - a[1] * b[0]; } export class Line { constructor( public readonly p: vec2, public readonly v: vec2, ) {} public getNormal(out: vec2): vec2 { return normal(out, this.v); } public projectPointDistance(p2: vec2): number { const v2 = vec2.sub(vec2.create(), p2, this.p); return vec2.dot(this.v, v2); } public projectPoint(out: vec2, p2: vec2): vec2 { const d = this.projectPointDistance(p2); return vec2.scaleAndAdd(out, this.p, this.v, d); } public distancePoint(p2: vec2): number { const v2 = vec2.sub(vec2.create(), p2, this.p); return crossz(this.v, v2); } public intersectLine(out: vec2, l2: Line): vec2 { const vp = vec2.sub(vec2.create(), l2.p, this.p); const d = crossz(vp, this.v); const d2 = d / crossz(this.v, l2.v); return vec2.scaleAndAdd(out, l2.p, l2.v, d2); } } export class Movement { public readonly v: vec2; constructor( public readonly p1: vec2, public readonly p2: vec2, ) { this.v = vec2.sub(vec2.create(), p2, p1); } public intersectLine(out: vec2, l: Line): vec2 { const vp = vec2.sub(vec2.create(), l.p, this.p1); const d = crossz(vp, this.v); const d2 = d / crossz(this.v, l.v); return vec2.scaleAndAdd(out, l.p, l.v, d2); } public passes(p: vec2): boolean { const vp = vec2.sub(vec2.create(), p, this.p1); const d = vec2.dot(this.v, vp); return d >= 0 && d <= vec2.sqrLen(this.v); } public toLineSegment(): LineSegment { return LineSegment.fromPoints(this.p1, this.p2); } public translate(t: vec2): Movement { const p1 = vec2.add(vec2.create(), this.p1, t); const p2 = vec2.add(vec2.create(), this.p2, t); return new Movement(p1, p2); } } export class LineSegment extends Line implements Collidable { public static fromPoints(p1: vec2, p2: vec2): LineSegment { const d = vec2.dist(p1, p2); const v = vec2.sub(vec2.create(), p2, p1); vec2.scale(v, v, 1 / d); return new LineSegment(p1, v, d); } constructor( p: vec2, v: vec2, public readonly l: number, ) { super(p, v); } public getP2(out: vec2): vec2 { return vec2.scaleAndAdd(out, this.p, this.v, this.l); } public containsPoint(p2: vec2): boolean { const d = this.projectPointDistance(p2); return (d >= 0 && d <= this.l); } public collide(out: vec2, move: Movement, r: number): boolean { if (this.distancePoint(move.p1) < 0) return false; if (crossz(move.v, this.v) < 0) return false; const t = this.getNormal(vec2.create()); vec2.scale(t, t, -r); const refMove = move.translate(t); if (!this.collideRef(out, refMove)) return false; vec2.sub(out, out, t); return true; } private collideRef(out: vec2, move: Movement): boolean { if (this.distancePoint(move.p2) >= 0) return false; const x = move.intersectLine(vec2.create(), this); if (!this.containsPoint(x)) return false; this.projectPoint(out, move.p2); return true; } }