78 lines
1.7 KiB
TypeScript
78 lines
1.7 KiB
TypeScript
import { lerp } from "./lib/lerp.ts";
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import type { Vector } from "./Vector.ts";
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export type Segment = [Vector, Vector];
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export type SegmentIntersection = {
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position: Vector;
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offset: number;
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};
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export function createSegmentIntersection(): SegmentIntersection {
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return {
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position: {
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x: Number.NaN,
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y: Number.NaN,
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},
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offset: Number.NaN,
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};
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}
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export function setSegmentIntersection(
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segmentIntersection: SegmentIntersection,
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a: Segment,
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b: Segment,
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): void {
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const bottom =
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(b[1].y - b[0].y) * (a[1].x - a[0].x) -
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(b[1].x - b[0].x) * (a[1].y - a[0].y);
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if (bottom === 0) {
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segmentIntersection.position.x = Number.NaN;
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segmentIntersection.position.y = Number.NaN;
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segmentIntersection.offset = Number.NaN;
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return;
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}
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const tTop =
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(b[1].x - b[0].x) * (a[0].y - b[0].y) -
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(b[1].y - b[0].y) * (a[0].x - b[0].x);
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const uTop =
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(b[0].y - a[0].y) * (a[0].x - a[1].x) -
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(b[0].x - a[0].x) * (a[0].y - a[1].y);
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const t = tTop / bottom;
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const u = uTop / bottom;
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if (t < 0 || t > 1 || u < 0 || u > 1) {
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segmentIntersection.position.x = Number.NaN;
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segmentIntersection.position.y = Number.NaN;
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segmentIntersection.offset = Number.NaN;
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return;
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}
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segmentIntersection.position.x = lerp(a[0].x, a[1].x, t);
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segmentIntersection.position.y = lerp(a[0].y, a[1].y, t);
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segmentIntersection.offset = t;
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}
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export function drawSegment(
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segment: Segment,
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ctx: CanvasRenderingContext2D,
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color: string = "#fff",
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alpha: number = 1.0,
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lineWidth: number = 1,
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): void {
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ctx.save();
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ctx.strokeStyle = color;
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ctx.globalAlpha = alpha;
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ctx.lineWidth = lineWidth;
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ctx.beginPath();
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ctx.moveTo(segment[0].x, segment[0].y);
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ctx.lineTo(segment[1].x, segment[1].y);
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ctx.stroke();
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ctx.restore();
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}
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