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import { mat2, vec2 } from 'gl-matrix';
const rot90 = mat2.fromRotation(mat2.create(), Math.PI / 2);
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 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);
}
}
export class LineSegment extends Line {
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 collidesPoint(p2: vec2): boolean {
const d = this.projectPointDistance(p2);
return (d >= 0 && d <= this.l);
}
public collidesMove(out: vec2, move: Movement): boolean {
if (this.distancePoint(move.p1) < 0)
return false;
if (this.distancePoint(move.p2) >= 0)
return false;
const x = move.intersectLine(vec2.create(), this);
if (!this.collidesPoint(x))
return false;
this.projectPoint(out, move.p2);
return true;
}
}
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