Inverse Kinematics: Dragging and Reaching - HTML5 Animation with JavaScript - page 323

segments = [],
numSegments = 5,
target; //referenced by drawFrame and move
while (numSegments--) {
segments.push(new Segment(50, 10));
}
//center the last one
segments[segments.length - 1].x = canvas.width / 2;
segments[segments.length - 1].y = canvas.height / 2;
function reach (segment, xpos, ypos) {
var dx = xpos - segment.x,
dy = ypos - segment.y;
segment.rotation = Math.atan2(dy, dx);
var w = segment.getPin().x - segment.x,
h = segment.getPin().y - segment.y;
return {
x: xpos - w,
y: ypos - h
};
}
function position (segmentA, segmentB) {
segmentA.x = segmentB.getPin().x;
segmentA.y = segmentB.getPin().y;
}
function move (segment, i) {
if (i !== 0) {
target = reach(segment, target.x, target.y);
position(segments[i - 1], segment);
}
}
function draw (segment) {
segment.draw(context);
}
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
target = reach(segments[0], mouse.x, mouse.y);
segments.forEach(move);
segments.forEach(draw);
}());
};