1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
|
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;
}
public isCollidingWith(box: BoundingBox): boolean {
// optimization; when neither rotates just check if they overlap
if (this.rotation == 0 && box.rotation == 0) {
const thisTopLeft = this.getTopLeft();
const thisBottomRight = this.getBottomRight();
const thatTopLeft = box.getTopLeft();
const thatBottomRight = box.getBottomRight();
if (
thisBottomRight.x <= thatTopLeft.x ||
thisTopLeft.x >= thatBottomRight.x ||
thisBottomRight.y <= thatTopLeft.y ||
thisTopLeft.y >= thatBottomRight.y
) {
return false;
}
return true;
}
// https://en.wikipedia.org/wiki/Hyperplane_separation_theorem
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)) // rotate
.map((vertex) => {
// translate
return {
x: vertex.x + this.center.x,
y: vertex.y + this.center.y,
};
});
}
public getRotationInPiOfUnitCircle(): number {
let rads = this.rotation * (Math.PI / 180);
if (rads >= Math.PI) {
// Physics system guarantees rotation \in [0, 360)
rads -= Math.PI;
}
return rads;
}
public getOutscribedBoxDims(): Dimension2D {
let rads = this.getRotationInPiOfUnitCircle();
const { width, height } = this.dimension;
if (rads == 0) return 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)),
};
}
public getTopLeft(): Coord2D {
return {
x: this.center.x - this.dimension.width / 2,
y: this.center.y - this.dimension.height / 2,
};
}
public getBottomRight(): Coord2D {
return {
x: this.center.x + this.dimension.width / 2,
y: this.center.y + this.dimension.height / 2,
};
}
}
|
