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86 lines
3.0 KiB
HTML
86 lines
3.0 KiB
HTML
5 years ago
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<!doctype html>
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<html>
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<head>
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<title>canvas.js | path points</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<script type="text/javascript" src="../../pattern/canvas.js"></script>
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</head>
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<body>
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<script type="text/canvas" loop="true">
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function setup(canvas) {
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canvas.size(500, 500);
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}
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function draw(canvas) {
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canvas.clear();
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nofill();
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stroke(0);
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// 1) Draw a curve.
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var p1 = new BezierPath();
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p1.moveto(20, 20);
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p1.curveto(100, 20, 100, 150, 200, 100);
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drawpath(p1);
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// A BezierPath contains a list of points along the path.
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// Each point pt has a property pt.cmd: MOVETO, LINETO, CURVETO or CLOSE.
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// Each point pt has pt.x and pt.y that define its location.
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for (var i=0; i < p1.array.length; i++) {
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var pt = p1.array[i];
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ellipse(pt.x, pt.y, 4, 4);
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text(pt.cmd, pt.x+4, pt.y-4, {fill: color(0)});
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// Each point has pt.ctrl1 and pt.ctrl2, its control handles.
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// pt.ctrl1 defines how the curve from the previous point started.
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// pt.ctrl2 defines how the curve from the previous point
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// arrives in this point.
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line(pt.x, pt.y, pt.ctrl2.x, pt.ctrl2.y);
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if (i > 0) {
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line(p1.array[i-1].x,
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p1.array[i-1].y,
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pt.ctrl1.x,
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pt.ctrl1.y, {stroke: color(1,0,0)}); // ctrl1 = red
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}
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}
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// 2) Draw a curve.
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var p2 = new BezierPath();
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p2.moveto(20, 120);
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p2.curveto(100, 120, 100, 250, 200, 200);
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drawpath(p2);
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// The method BezierPath.point() calculates a "dynamic" point,
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// located at a given time (0.0-1.0) on the path.
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var t = canvas.frame % 100 * 0.01; // from 0 to 1 in 100 frames...
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var pt = p2.point(t);
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ellipse(pt.x, pt.y, 4, 4);
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text(Math.round(t,2), pt.x, pt.y, {fill: color(0)});
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// With a dynamic point the handles are interpreted differently:
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// pt.ctrl1 defines how the curve arrives, and
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// pt.ctrl2 defines how it continues to the next point.
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line(pt.x, pt.y, pt.ctrl1.x, pt.ctrl1.y, {stroke: color(1,0,0)});
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line(pt.x, pt.y, pt.ctrl2.x, pt.ctrl2.y);
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// 3) Draw an ellipse.
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var p3 = new BezierPath();
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p3.ellipse(350, 200, 150, 150);
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drawpath(p3);
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// directed() takes a list of points and a function(angle, pt).
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// It loops over each point and its "direction" along the path.
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directed(p3.points(20, {start: 0.001, end: 1-1/20}),
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function(angle, pt) {
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push();
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translate(pt.x, pt.y);
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rotate(angle - 90); // angle-90 = perpendicular
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line(0, 0, 20, 0);
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pop();
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}
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);
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// Note the optional parameters "start" and "end" in BezierPath.points().
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// With start=0.0 and end=1.0 (default),
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// the points are spread out equally from the start of the path to the end.
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// If the path is closed (e.g., ellipse), the first and last point overlap.
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// end = 1 - (1 / amount) omits the last (overlapping) point.
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// start = 0.001 skips the initial moveto() in the path.
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// This ensures that the generated point has control handles,
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// which are used to calculate its angle in directed().
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}
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</script>
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</body>
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</html>
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