/**
* Adjusts the parent and child bone rotations so the tip of the child is as close to the target
* position as possible. The target is specified in the world coordinate system.
*
* @param child Any descendant bone of the parent.
*/
public static void apply(
Bone parent, Bone child, float targetX, float targetY, int bendDirection, float alpha) {
float childRotation = child.rotation, parentRotation = parent.rotation;
if (alpha == 0) {
child.rotationIK = childRotation;
parent.rotationIK = parentRotation;
return;
}
Vector2 position = temp;
Bone parentParent = parent.parent;
if (parentParent != null) {
parentParent.worldToLocal(position.set(targetX, targetY));
targetX = (position.x - parent.x) * parentParent.worldScaleX;
targetY = (position.y - parent.y) * parentParent.worldScaleY;
} else {
targetX -= parent.x;
targetY -= parent.y;
}
if (child.parent == parent) position.set(child.x, child.y);
else parent.worldToLocal(child.parent.localToWorld(position.set(child.x, child.y)));
float childX = position.x * parent.worldScaleX, childY = position.y * parent.worldScaleY;
float offset = (float) Math.atan2(childY, childX);
float len1 = (float) Math.sqrt(childX * childX + childY * childY),
len2 = child.data.length * child.worldScaleX;
// Based on code by Ryan Juckett with permission: Copyright (c) 2008-2009 Ryan Juckett,
// http://www.ryanjuckett.com/
float cosDenom = 2 * len1 * len2;
if (cosDenom < 0.0001f) {
child.rotationIK =
childRotation
+ ((float) Math.atan2(targetY, targetX) * radDeg - parentRotation - childRotation)
* alpha;
return;
}
float cos =
clamp(
(targetX * targetX + targetY * targetY - len1 * len1 - len2 * len2) / cosDenom, -1, 1);
float childAngle = (float) Math.acos(cos) * bendDirection;
float adjacent = len1 + len2 * cos, opposite = len2 * sin(childAngle);
float parentAngle =
(float)
Math.atan2(
targetY * adjacent - targetX * opposite, targetX * adjacent + targetY * opposite);
float rotation = (parentAngle - offset) * radDeg - parentRotation;
if (rotation > 180) rotation -= 360;
else if (rotation < -180) //
rotation += 360;
parent.rotationIK = parentRotation + rotation * alpha;
rotation = (childAngle + offset) * radDeg - childRotation;
if (rotation > 180) rotation -= 360;
else if (rotation < -180) //
rotation += 360;
child.rotationIK =
childRotation + (rotation + parent.worldRotation - child.parent.worldRotation) * alpha;
}
public void update() {
float rotateMix = this.rotateMix,
translateMix = this.translateMix,
scaleMix = this.scaleMix,
shearMix = this.shearMix;
Bone target = this.target;
float ta = target.a, tb = target.b, tc = target.c, td = target.d;
float degRadReflect = ta * td - tb * tc > 0 ? degRad : -degRad;
float offsetRotation = data.offsetRotation * degRadReflect,
offsetShearY = data.offsetShearY * degRadReflect;
Array<Bone> bones = this.bones;
for (int i = 0, n = bones.size; i < n; i++) {
Bone bone = bones.get(i);
boolean modified = false;
if (rotateMix != 0) {
float a = bone.a, b = bone.b, c = bone.c, d = bone.d;
float r = atan2(tc, ta) - atan2(c, a) + offsetRotation;
if (r > PI) r -= PI2;
else if (r < -PI) r += PI2;
r *= rotateMix;
float cos = cos(r), sin = sin(r);
bone.a = cos * a - sin * c;
bone.b = cos * b - sin * d;
bone.c = sin * a + cos * c;
bone.d = sin * b + cos * d;
modified = true;
}
if (translateMix != 0) {
Vector2 temp = this.temp;
target.localToWorld(temp.set(data.offsetX, data.offsetY));
bone.worldX += (temp.x - bone.worldX) * translateMix;
bone.worldY += (temp.y - bone.worldY) * translateMix;
modified = true;
}
if (scaleMix > 0) {
float s = (float) Math.sqrt(bone.a * bone.a + bone.c * bone.c);
float ts = (float) Math.sqrt(ta * ta + tc * tc);
if (s > 0.00001f) s = (s + (ts - s + data.offsetScaleX) * scaleMix) / s;
bone.a *= s;
bone.c *= s;
s = (float) Math.sqrt(bone.b * bone.b + bone.d * bone.d);
ts = (float) Math.sqrt(tb * tb + td * td);
if (s > 0.00001f) s = (s + (ts - s + data.offsetScaleY) * scaleMix) / s;
bone.b *= s;
bone.d *= s;
modified = true;
}
if (shearMix > 0) {
float b = bone.b, d = bone.d;
float by = atan2(d, b);
float r = atan2(td, tb) - atan2(tc, ta) - (by - atan2(bone.c, bone.a));
if (r > PI) r -= PI2;
else if (r < -PI) r += PI2;
r = by + (r + offsetShearY) * shearMix;
float s = (float) Math.sqrt(b * b + d * d);
bone.b = cos(r) * s;
bone.d = sin(r) * s;
modified = true;
}
if (modified) bone.appliedValid = false;
}
}