85 lines
3.0 KiB
JavaScript
85 lines
3.0 KiB
JavaScript
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function interp(A, B, t) {
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return A + (B - A) * t;
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}
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function interp_cubic_coords(x1, x2, x3, x4, t)
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{
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var ab = interp(x1, x2, t);
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var bc = interp(x2, x3, t);
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var cd = interp(x3, x4, t);
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var abc = interp(ab, bc, t);
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var bcd = interp(bc, cd, t);
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var abcd = interp(abc, bcd, t);
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return abcd;
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}
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// FIXME : only works for path with single cubic
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function path_partial(value, path) {
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assert(isArray(path));
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var out = [];
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for (var cIndex = 0; cIndex < path.length; ++cIndex) {
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out[cIndex] = {};
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var curveKey = Object.keys(path[cIndex])[0];
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var curve = path[cIndex][curveKey];
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var outArray;
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switch (curveKey) {
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case "cubic":
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var x1 = curve[0], y1 = curve[1], x2 = curve[2], y2 = curve[3];
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var x3 = curve[4], y3 = curve[5], x4 = curve[6], y4 = curve[7];
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var t1 = 0, t2 = value;
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var ax = interp_cubic_coords(x1, x2, x3, x4, t1);
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var ay = interp_cubic_coords(y1, y2, y3, y4, t1);
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var ex = interp_cubic_coords(x1, x2, x3, x4, (t1*2+t2)/3);
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var ey = interp_cubic_coords(y1, y2, y3, y4, (t1*2+t2)/3);
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var fx = interp_cubic_coords(x1, x2, x3, x4, (t1+t2*2)/3);
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var fy = interp_cubic_coords(y1, y2, y3, y4, (t1+t2*2)/3);
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var dx = interp_cubic_coords(x1, x2, x3, x4, t2);
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var dy = interp_cubic_coords(y1, y2, y3, y4, t2);
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var mx = ex * 27 - ax * 8 - dx;
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var my = ey * 27 - ay * 8 - dy;
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var nx = fx * 27 - ax - dx * 8;
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var ny = fy * 27 - ay - dy * 8;
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var bx = (mx * 2 - nx) / 18;
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var by = (my * 2 - ny) / 18;
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var cx = (nx * 2 - mx) / 18;
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var cy = (ny * 2 - my) / 18;
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outArray = [
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ax, ay, bx, by, cx, cy, dx, dy
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];
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break;
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default:
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assert(0); // unimplemented
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}
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out[cIndex][curveKey] = outArray;
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}
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return out;
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}
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function interp_paths(value, paths) {
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assert(isArray(paths));
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assert(paths.length == 2);
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var curves0 = paths[0];
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assert(isArray(curves0));
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var curves1 = paths[1];
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assert(isArray(curves1));
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assert(curves0.length == curves1.length);
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var out = [];
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for (var cIndex = 0; cIndex < curves0.length; ++cIndex) {
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out[cIndex] = {};
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var curve0Key = Object.keys(curves0[cIndex])[0];
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var curve1Key = Object.keys(curves1[cIndex])[0];
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assert(curve0Key == curve1Key);
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var curve0 = curves0[cIndex][curve0Key];
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var curve1 = curves1[cIndex][curve1Key];
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assert(isArray(curve0));
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assert(isArray(curve1));
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assert(curve0.length == curve1.length);
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var outArray = [];
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for (var i = 0; i < curve1.length; ++i) {
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outArray[i] = curve0[i] + (curve1[i] - curve0[i]) * value;
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}
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out[cIndex][curve0Key] = outArray;
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}
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return out;
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}
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