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