73 lines
1.5 KiB
Markdown
73 lines
1.5 KiB
Markdown
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---
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title: curveIntersectsY()
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---
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```js
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array | Point | false utils.curveIntersectsY(
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Point start,
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Point cp1,
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Point cp2,
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Point end,
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float y)
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```
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Finds the point(s) where a curve intersects a given Y-value.
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This is a low-level variant
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of [`Path.intersectsY()`](/en/docs/developer/api/path/#pathintersectsy).
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Instead of a path, you describe a single curve by passing the four
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points that describes it.
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This returns `false` if no intersections are found,
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a [Point](/en/docs/developer/api/point/) object if
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a single intersection is found, and an array
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of [Point](/en/docs/developer/api/point/) objects if
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multiple intersections are found.
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<Example part="utils_curveintersectsy" caption="A Utils.curveIntersectY() example" />
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```js
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let {
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Point,
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points,
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Path,
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paths,
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utils,
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snippets,
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Snippet
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} = part.shorthand();
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points.start = new Point(10, 45);
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points.cp1 = new Point(50, 10);
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points.cp2 = new Point(0, 80);
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points.end = new Point(110, 70);
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paths.curve = new Path()
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.move(points.start)
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.curve(points.cp1, points.cp2, points.end);
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for (let y of [40, 50]) {
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points["from" + y] = new Point(10, y);
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points["to" + y] = new Point(110, y);
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paths["line" + y] = new Path()
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.move(points["from" + y])
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.line(points["to" + y])
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.attr("class", "lining dashed");
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}
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snippets.i50 = new Snippet(
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"notch",
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utils.curveIntersectsY(points.start, points.cp1, points.cp2, points.end, 50)
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);
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for (let p of utils.curveIntersectsY(
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points.start,
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points.cp1,
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points.cp2,
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points.end,
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40
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))
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snippets[p.x] = new Snippet("notch", p);
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```
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