void spIkConstraint_apply1 (spBone* bone, float targetX, float targetY, float alpha) {
spBone* pp = bone->parent;
float id = 1 / (pp->a * pp->d - pp->b * pp->c);
float x = targetX - pp->worldX, y = targetY - pp->worldY;
float tx = (x * pp->d - y * pp->b) * id - bone->x, ty = (y * pp->a - x * pp->c) * id - bone->y;
float rotationIK = ATAN2(ty, tx) * RAD_DEG - bone->shearX - bone->rotation;
if (bone->scaleX < 0) rotationIK += 180;
if (rotationIK > 180) rotationIK -= 360;
else if (rotationIK < -180) rotationIK += 360;
spBone_updateWorldTransformWith(bone, bone->x, bone->y, bone->rotation + rotationIK * alpha, bone->scaleX,
bone->scaleY, bone->shearX, bone->shearY);
}
void spBone_updateWorldTransform (spBone* self) {
spBone_updateWorldTransformWith(self, self->x, self->y, self->rotation, self->scaleX, self->scaleY, self->shearX, self->shearY);
}
void spIkConstraint_apply2 (spBone* parent, spBone* child, float targetX, float targetY, int bendDir, float alpha) {
float px = parent->x, py = parent->y, psx = parent->scaleX, psy = parent->scaleY;
float cx = child->x, cy, csx = child->scaleX, cwx, cwy;
int o1, o2, s2, u;
spBone* pp = parent->parent;
float tx, ty, dx, dy, l1, l2, a1, a2, r;
float id, x, y;
if (alpha == 0) {
spBone_updateWorldTransform(child);
return;
}
if (psx < 0) {
psx = -psx;
o1 = 180;
s2 = -1;
} else {
o1 = 0;
s2 = 1;
}
if (psy < 0) {
psy = -psy;
s2 = -s2;
}
if (csx < 0) {
csx = -csx;
o2 = 180;
} else
o2 = 0;
r = psx - psy;
u = (r < 0 ? -r : r) <= 0.0001f;
if (!u) {
cy = 0;
cwx = parent->a * cx + parent->worldX;
cwy = parent->c * cx + parent->worldY;
} else {
cy = child->y;
cwx = parent->a * cx + parent->b * cy + parent->worldX;
cwy = parent->c * cx + parent->d * cy + parent->worldY;
}
id = 1 / (pp->a * pp->d - pp->b * pp->c);
x = targetX - pp->worldX;
y = targetY - pp->worldY;
tx = (x * pp->d - y * pp->b) * id - px;
ty = (y * pp->a - x * pp->c) * id - py;
x = cwx - pp->worldX;
y = cwy - pp->worldY;
dx = (x * pp->d - y * pp->b) * id - px;
dy = (y * pp->a - x * pp->c) * id - py;
l1 = SQRT(dx * dx + dy * dy);
l2 = child->data->length * csx;
if (u) {
float cosine, a, b;
l2 *= psx;
cosine = (tx * tx + ty * ty - l1 * l1 - l2 * l2) / (2 * l1 * l2);
if (cosine < -1) cosine = -1;
else if (cosine > 1) cosine = 1;
a2 = ACOS(cosine) * bendDir;
a = l1 + l2 * cosine;
b = l2 * SIN(a2);
a1 = ATAN2(ty * a - tx * b, tx * a + ty * b);
} else {
float a = psx * l2, b = psy * l2;
float aa = a * a, bb = b * b, ll = l1 * l1, dd = tx * tx + ty * ty, ta = ATAN2(ty, tx);
float c0 = bb * ll + aa * dd - aa * bb, c1 = -2 * bb * l1, c2 = bb - aa;
float d = c1 * c1 - 4 * c2 * c0;
float minAngle = 0, minDist = FLT_MAX, minX = 0, minY = 0;
float maxAngle = 0, maxDist = 0, maxX = 0, maxY = 0;
float x = l1 + a, dist = x * x, angle, y;
if (d >= 0) {
float q = SQRT(d), r0, r1;
if (c1 < 0) q = -q;
q = -(c1 + q) / 2;
r0 = q / c2; r1 = c0 / q;
r = ABS(r0) < ABS(r1) ? r0 : r1;
if (r * r <= dd) {
y = SQRT(dd - r * r) * bendDir;
a1 = ta - ATAN2(y, r);
a2 = ATAN2(y / psy, (r - l1) / psx);
goto outer;
}
}
if (dist > maxDist) {
maxAngle = 0;
maxDist = dist;
maxX = x;
}
x = l1 - a;
dist = x * x;
if (dist < minDist) {
minAngle = PI;
minDist = dist;
minX = x;
}
angle = ACOS(-a * l1 / (aa - bb));
x = a * COS(angle) + l1;
y = b * SIN(angle);
dist = x * x + y * y;
if (dist < minDist) {
minAngle = angle;
minDist = dist;
minX = x;
minY = y;
}
if (dist > maxDist) {
maxAngle = angle;
maxDist = dist;
maxX = x;
maxY = y;
}
if (dd <= (minDist + maxDist) / 2) {
a1 = ta - ATAN2(minY * bendDir, minX);
a2 = minAngle * bendDir;
} else {
a1 = ta - ATAN2(maxY * bendDir, maxX);
a2 = maxAngle * bendDir;
}
}
outer: {
float os = ATAN2(cy, cx) * s2;
a1 = (a1 - os) * RAD_DEG + o1 - parent->rotation;
if (a1 > 180) a1 -= 360;
else if (a1 < -180) a1 += 360;
spBone_updateWorldTransformWith(parent, px, py, parent->rotation + a1 * alpha, parent->scaleX, parent->scaleY, 0, 0);
a2 = ((a2 + os) * RAD_DEG - child->shearX) * s2 + o2 - child->rotation;
if (a2 > 180) a2 -= 360;
else if (a2 < -180) a2 += 360;
spBone_updateWorldTransformWith(child, cx, cy, child->rotation + a2 * alpha, child->scaleX, child->scaleY, child->shearX, child->shearY);
}
}