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cf97610067
* extract canvasDrawPoints and use new_last_points. * lint fix. * canvasDrawPoints default percent 1,
57 lines
2.1 KiB
TypeScript
57 lines
2.1 KiB
TypeScript
/* eslint-disable */
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export interface Point {
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x: number
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y: number
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}
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// movement: percent is 0-1
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export function getMovementXYatPercent(p: Point[], percent: number): Point {
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const len = p.length
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if (len == 0) {
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console.error('getMovementXYatPercent: no points specified');
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return { x:0, y:0 }
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}
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if (len == 1) return p[0]
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if (len == 2) return getLineXYatPercent(p[0], p[1], percent)
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if (len == 3) return getQuadraticBezierXYatPercent(p[0], p[1], p[2], percent)
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if (len == 4) return getCubicBezierXYatPercent(p[0], p[1], p[2], p[3], percent)
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// TODO: Support more than 4 points
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if (len-1 % 3 == 0) return getCubicBezierXYatPercent(p[0], p[(len-1)/3], p[((len-1)/3)*2], p[len-1], percent)
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else if (len-1 % 2 == 0) return getQuadraticBezierXYatPercent(p[0], p[(len-1)/2], p[len-1], percent)
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else return getLineXYatPercent(p[0], p[len-1], percent)
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}
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// line: percent is 0-1
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export function getLineXYatPercent(startPt: Point, endPt: Point, percent: number) : Point {
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return {
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x: startPt.x + (endPt.x - startPt.x) * percent,
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y: startPt.y + (endPt.y - startPt.y) * percent,
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};
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}
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// quadratic bezier: percent is 0-1
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export function getQuadraticBezierXYatPercent(startPt: Point, controlPt: Point, endPt: Point, percent: number): Point {
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return {
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x: Math.pow(1 - percent, 2) * startPt.x + 2 * (1 - percent) * percent * controlPt.x + Math.pow(percent, 2) * endPt.x,
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y: Math.pow(1 - percent, 2) * startPt.y + 2 * (1 - percent) * percent * controlPt.y + Math.pow(percent, 2) * endPt.y,
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}
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}
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// cubic bezier percent is 0-1
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export function getCubicBezierXYatPercent(startPt: Point, controlPt1: Point, controlPt2: Point, endPt: Point, percent: number): Point {
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return {
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x: cubicN(percent, startPt.x, controlPt1.x, controlPt2.x, endPt.x),
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y: cubicN(percent, startPt.y, controlPt1.y, controlPt2.y, endPt.y),
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}
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}
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// cubic helper formula at percent distance
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function cubicN(pct: number, a: number, b: number, c: number, d: number): number {
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var t2 = pct * pct;
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var t3 = t2 * pct;
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return a + (-a * 3 + pct * (3 * a - a * pct)) * pct + (3 * b + pct * (-6 * b + b * 3 * pct)) * pct + (c * 3 - c * 3 * pct) * t2 + d * t3;
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}
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