jumpstorm/engine/components/BoundingBox.ts

85 lines
2.5 KiB
TypeScript

import { Component, ComponentNames } from ".";
import type { Coord2D, Dimension2D } from "../interfaces";
import { dotProduct, rotateVector } from "../utils";
export class BoundingBox extends Component {
public center: Coord2D;
public dimension: Dimension2D;
public rotation: number;
constructor(center: Coord2D, dimension: Dimension2D, rotation?: number) {
super(ComponentNames.BoundingBox);
this.center = center;
this.dimension = dimension;
this.rotation = rotation ?? 0;
}
// https://en.wikipedia.org/wiki/Hyperplane_separation_theorem
public isCollidingWith(box: BoundingBox): boolean {
const boxes = [this.getVertices(), box.getVertices()];
for (const poly of boxes) {
for (let i = 0; i < poly.length; i++) {
const [A, B] = [poly[i], poly[(i + 1) % poly.length]];
const normal: Coord2D = { x: B.y - A.y, y: A.x - B.x };
const [[minThis, maxThis], [minBox, maxBox]] = boxes.map((box) =>
box.reduce(
([min, max], vertex) => {
const projection = dotProduct(normal, vertex);
return [Math.min(min, projection), Math.max(max, projection)];
},
[Infinity, -Infinity],
),
);
if (maxThis < minBox || maxBox < minThis) return false;
}
}
return true;
}
public getVertices(): Coord2D[] {
return [
{ x: -this.dimension.width / 2, y: -this.dimension.height / 2 },
{ x: -this.dimension.width / 2, y: this.dimension.height / 2 },
{ x: this.dimension.width / 2, y: this.dimension.height / 2 },
{ x: this.dimension.width / 2, y: -this.dimension.height / 2 },
]
.map((vertex) => rotateVector(vertex, this.rotation))
.map((vertex) => {
return {
x: vertex.x + this.center.x,
y: vertex.y + this.center.y,
};
});
}
public getRotationInPiOfUnitCircle() {
let rads = this.rotation * (Math.PI / 180);
if (rads >= Math.PI) {
rads -= Math.PI;
}
return rads;
}
public getOutscribedBoxDims(): Dimension2D {
let rads = this.getRotationInPiOfUnitCircle();
const { width, height } = this.dimension;
if (rads <= Math.PI / 2) {
return {
width: Math.abs(height * Math.sin(rads) + width * Math.cos(rads)),
height: Math.abs(width * Math.sin(rads) + height * Math.cos(rads)),
};
}
rads -= Math.PI / 2;
return {
width: Math.abs(height * Math.cos(rads) + width * Math.sin(rads)),
height: Math.abs(width * Math.cos(rads) + height * Math.sin(rads)),
};
}
}