private void doSimpleSolver()
//
// Solve single joint in the x-y plane
//
// - first it calculates the angle between the handle and the end-effector.
// - then it determines which way to rotate the joint.
//
{
// Get the handle and create a function set for it
//
MIkHandleGroup handle_group = handleGroup;
if (null == handle_group)
{
throw new System.InvalidOperationException("invalid handle group.");
}
MObject handle = handle_group.handle(0);
MDagPath handlePath = MDagPath.getAPathTo(handle);
MFnIkHandle fnHandle = new MFnIkHandle(handlePath);
// Get the position of the end_effector
//
MDagPath end_effector = new MDagPath();
fnHandle.getEffector(end_effector);
MFnTransform tran = new MFnTransform(end_effector);
MPoint effector_position = tran.rotatePivot(MSpace.Space.kWorld);
// Get the position of the handle
//
MPoint handle_position = fnHandle.rotatePivot(MSpace.Space.kWorld);
// Get the start joint position
//
MDagPath start_joint = new MDagPath();
fnHandle.getStartJoint(start_joint);
MFnTransform start_transform = new MFnTransform(start_joint);
MPoint start_position = start_transform.rotatePivot(MSpace.Space.kWorld);
// Calculate the rotation angle
//
MVector v1 = start_position.minus(effector_position);
MVector v2 = start_position.minus(handle_position);
double angle = v1.angle(v2);
// -------- Figure out which way to rotate --------
//
// define two vectors U and V as follows
// U = EndEffector(E) - StartJoint(S)
// N = Normal to U passing through EndEffector
//
// Clip handle_position to half-plane U to determine the region it
// lies in. Use the region to determine the rotation direction.
//
// U
// ^ Region Rotation
// | B
// (E)---N A C-C-W
// A | B C-W
// | B
// |
// (S)
//
double rot = 0.0; // Rotation about Z-axis
// U and N define a half-plane to clip the handle against
//
MVector U = effector_position.minus(start_position);
U.normalize();
// Get a normal to U
//
MVector zAxis = new MVector(0.0, 0.0, 1.0);
MVector N = U.crossProduct(zAxis); // Cross product
N.normalize();
// P is the handle position vector
//
MVector P = handle_position.minus(effector_position);
// Determine the rotation direction
//
double PdotN = P[0] * N[0] + P[1] * N[1];
if (PdotN < 0)
{
// counter-clockwise
rot = angle;
}
else
{
// clockwise
rot = -1.0 * angle;
}
// get and set the Joint Angles
//
MDoubleArray jointAngles = new MDoubleArray();
getJointAngles(jointAngles);
jointAngles.set(jointAngles[0] + rot, 0);
setJointAngles(jointAngles);
}