43 lines
869 B
TypeScript
43 lines
869 B
TypeScript
export type Span = { entry: number; exit: number };
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/**
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* When is a point at `p`, moving by `v` over the frame, inside [min, max]?
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*
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* Returns the entry/exit times (t, where the position is p + v*t).
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* `entry` is always <= `exit`. Values may be < 0 or > 1.
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*
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* Special case: if v === 0, return {entry:-Infinity, exit:Infinity} when the
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* point is already inside [min, max], otherwise return null.
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*/
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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 isInBetween(p, min, max)
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? {
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entry: -Infinity,
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exit: +Infinity,
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}
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: 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 {
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entry: t1,
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exit: t2,
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};
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}
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function isInBetween(p: number, min: number, max: number): boolean {
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return min <= p && p <= max;
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}
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