64 lines
1.9 KiB
TypeScript
64 lines
1.9 KiB
TypeScript
// The whole kernel you've built, steps 01-09, finished. Reuse it.
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export type Vec = { x: number; y: number };
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export type AABB = { x: number; y: number; w: number; h: number };
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export type Span = { entry: number; exit: number };
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export type Hit = { time: number; normal: Vec };
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/** A hair of slack so we stop just short of a wall instead of inside it. */
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export const EPSILON = 1e-4;
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export const vec = (x: number, y: number): Vec => ({ x, y });
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export const add = (a: Vec, b: Vec): Vec => ({ x: a.x + b.x, y: a.y + b.y });
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export const sub = (a: Vec, b: Vec): Vec => ({ x: a.x - b.x, y: a.y - b.y });
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export const scale = (a: Vec, s: number): Vec => ({ x: a.x * s, y: a.y * s });
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export const dot = (a: Vec, b: Vec): number => a.x * b.x + a.y * b.y;
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export function sweepInterval(
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p: number,
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v: number,
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min: number,
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max: number,
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): Span | null {
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if (v === 0) {
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return min <= p && p <= max ? { entry: -Infinity, exit: Infinity } : null;
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}
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let t1 = (min - p) / v;
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let t2 = (max - p) / v;
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if (t1 > t2) {
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[t1, t2] = [t2, t1];
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}
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return { entry: t1, exit: t2 };
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}
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export function rayVsAABB(p: Vec, v: Vec, box: AABB): Hit | null {
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const spanX = sweepInterval(p.x, v.x, box.x, box.x + box.w);
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const spanY = sweepInterval(p.y, v.y, box.y, box.y + box.h);
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if (spanX === null || spanY === null) {
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return null;
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}
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const entry = Math.max(spanX.entry, spanY.entry);
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const exit = Math.min(spanX.exit, spanY.exit);
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if (entry > exit || entry >= 1 || exit <= 0) {
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return null;
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}
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const normal =
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spanX.entry > spanY.entry
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? { x: v.x > 0 ? -1 : 1, y: 0 }
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: { x: 0, y: v.y > 0 ? -1 : 1 };
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return { time: entry, normal };
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}
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export function sweptAABB(a: AABB, v: Vec, b: AABB): Hit | null {
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const inflated: AABB = {
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x: b.x - a.w,
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y: b.y - a.h,
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w: b.w + a.w,
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h: b.h + a.h,
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};
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return rayVsAABB({ x: a.x, y: a.y }, v, inflated);
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}
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export function slide(v: Vec, normal: Vec): Vec {
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return sub(v, scale(normal, dot(v, normal)));
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}
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