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import { Component, ComponentNames } from ".";
import type { Coord2D, Dimension2D } from "../interfaces";
import { dotProduct, rotateVector, normalizeVector } 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;
}
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,
};
});
}
private getAxes() {
const corners: Coord2D[] = this.getVerticesRelativeToCenter();
const axes: Coord2D[] = [];
for (let i = 0; i < corners.length; ++i) {
const [cornerA, cornerB] = [
corners[i],
corners[(i + 1) % corners.length],
].map((corner) => rotateVector(corner, this.rotation));
axes.push(
normalizeVector({
x: cornerB.y - cornerA.y,
y: -(cornerB.x - cornerA.x),
})
);
}
return axes;
}
private project(axis: Coord2D): [number, number] {
const corners = this.getCornersRelativeToCenter();
let [min, max] = [Infinity, -Infinity];
for (const corner of corners) {
const rotated = rotateVector(corner, this.rotation);
const translated = {
x: rotated.x + this.center.x,
y: rotated.y + this.center.y,
};
const projection = dotProduct(translated, axis);
min = Math.min(projection, min);
max = Math.max(projection, max);
}
return [min, max];
}
}
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