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import java.awt.*;
import java.awt.event.*;
public class trackball extends MouseAdapter implements MouseMotionListener{
private final float trackballSize;
private int prevX = 0;
private int prevY = 0;
private int startX = 0;
private int startY = 0;
private float[] curQuat = buildQuaternion(0.0f, 0.0f, 0.0f, 0.0f);
private float[] lastQuat = curQuat;
private boolean spin = false;
public trackball(){
trackballSize = 0.8f;
}
/** specify component virtual trackball is in */
public void listen(Component component){
component.addMouseListener(this);
component.addMouseMotionListener(this);
}
/** return rotation Matrix representing current rotation of trackball */
public float[] getRotMatrix() {
float[] rotMat = buildMatrix(curQuat);
if(spin){
curQuat = addQuats(lastQuat, curQuat);
}
return rotMat;
}
// deal with Mouse events
final static int EPS2 = 25; //only spin if mouse moved this far
public void mouseReleased(MouseEvent evt){
int dx = startX - evt.getX();
int dy = startY - evt.getY();
spin = (dx*dx + dy*dy > EPS2) ;
}
public void mousePressed(MouseEvent evt){
startX = prevX = evt.getX();
startY = prevY = evt.getY();
spin = false;
}
public void mouseMoved(MouseEvent evt){
}
public void mouseDragged(MouseEvent evt){
int aWidth = evt.getComponent().getSize().width;
int aHeight = evt.getComponent().getSize().height;
int currX = evt.getX();
int currY = evt.getY();
lastQuat =
buildQuaternion((float) (2.0f*prevX-aWidth)/(float) aWidth,
(float) (aHeight-2.0f*prevY)/(float) aHeight,
(float) (2.0f*currX-aWidth)/(float) aWidth,
(float) (aHeight -2.0f*currY)/(float) aHeight
);
curQuat = addQuats(lastQuat, curQuat);
prevX = currX;
prevY = currY;
}
/*
* Ok, simulate a track-ball. Project the points onto the virtual
* trackball, then figure out the axis of rotation, which is the cross
* product of P1 P2 and O P1 (O is the center of the ball, 0,0,0)
* Note: This is a deformed trackball-- is a trackball in the center,
* but is deformed into a hyperbolic sheet of rotation away from the
* center. This particular function was chosen after trying out
* several variations.
*
* It is assumed that the arguments to this routine are in the range
* (-1.0 ... 1.0)
*/
public float[] buildQuaternion(float p1x, float p1y, float p2x, float p2y) {
float[] a = new float[3]; /* Axis of rotation */
float phi; /* how much to rotate about axis */
float[] p1 = new float[3];
float[] p2 = new float[3];
float[] d = new float[3];
float t;
if (p1x == p2x && p1y == p2y) {
/* Zero rotation */
float[] q = {0.0f,0.0f,0.0f,1.0f};
return q;
}
/*
* First, figure out z-coordinates for projection of P1 and P2 to
* deformed sphere
*/
vset(p1,p1x,p1y,projectToSphere(trackballSize,p1x,p1y));
vset(p2,p2x,p2y,projectToSphere(trackballSize,p2x,p2y));
/*
* Now, we want the cross product of P1 and P2
*/
vcross(p2,p1,a);
/*
* Figure out how much to rotate around that axis.
*/
vsub(p1,p2,d);
t = vlength(d) / (2.0f*trackballSize);
/*
* Avoid problems with out-of-control values...
*/
if (t > 1.0) t = 1.0f;
if (t < -1.0) t = -1.0f;
phi = 2.0f * (float)Math.asin(t);
return axisToQuat(a,phi);
}
/** Create a unit quaternion that represents the rotation about axis
by theta */
public float[] axisToQuat(float[] axis, float theta){
float[] q = new float[4];
q[3] = (float)Math.cos(theta/2.0f); //scalar part
vnormal(axis);
vcopy(axis,q);
vscale(q,(float) Math.sin(theta/2.0));
return q;
}
public float[] renormalizeQuat(float[] q){
float len = 0.0f;
for (int i = 0; i < q.length; i++){
len += q[i]*q[i];
}
len = (float)Math.sqrt(len);
float[] ans = new float[q.length];
for (int i = 0; i < q.length; i++){
ans[i] = q[i]/len;
}
return ans;
}
/**
* Given two rotations, e1 and e2, expressed as quaternion rotations,
* figure out the equivalent single rotation and stuff it into dest.
*
* This routine also normalizes the result every RENORMCOUNT times it is
* called, to keep error from creeping in.
*
* NOTE: This routine is written so that q1 or q2 may be the same
* as dest (or each other).
*/
private static final int RENORMCOUNT= 97;
private int count=0;
public float[] addQuats(float[] q1, float[] q2){
float[] ans = new float[4];
ans[3] = q2[3]*q1[3] - q2[0]*q1[0] - q2[1]*q1[1] - q2[2]*q1[2];
ans[0] = q2[3]*q1[0] + q2[0]*q1[3] + q2[1]*q1[2] - q2[2]*q1[1];
ans[1] = q2[3]*q1[1] + q2[1]*q1[3] + q2[2]*q1[0] - q2[0]*q1[2];
ans[2] = q2[3]*q1[2] + q2[2]*q1[3] + q2[0]*q1[1] - q2[1]*q1[0];
if (++count > RENORMCOUNT) {
count = 0;
renormalizeQuat(ans);
}
return ans;
}
/**
* Project an x,y pair onto a sphere of radius r OR a hyperbolic sheet
* if we are away from the center of the sphere.
*/
public float projectToSphere(float r, float x, float y){
float z;
float d = (float)Math.sqrt(x*x + y*y);
if (d < r * 0.70710678118654752440f) { /* Inside sphere */
z = (float)Math.sqrt(r*r - d*d);
} else { /* On hyperbola */
float t = r / 1.41421356237309504880f;
z = t*t / d;
}
return z;
}
/*
* Build a rotation matrix, given a quaternion rotation.
*
*/
public float[] buildMatrix(float q[]) {
float[] m = new float[16];
m[0] = 1.0f - 2.0f * (q[1] * q[1] + q[2] * q[2]);
m[1] = 2.0f * (q[0] * q[1] - q[2] * q[3]);
m[2] = 2.0f * (q[2] * q[0] + q[1] * q[3]);
m[3] = 0.0f;
m[4] = 2.0f * (q[0] * q[1] + q[2] * q[3]);
m[5]= 1.0f - 2.0f * (q[2] * q[2] + q[0] * q[0]);
m[6] = 2.0f * (q[1] * q[2] - q[0] * q[3]);
m[7] = 0.0f;
m[8] = 2.0f * (q[2] * q[0] - q[1] * q[3]);
m[9] = 2.0f * (q[1] * q[2] + q[0] * q[3]);
m[10] = 1.0f - 2.0f * (q[1] * q[1] + q[0] * q[0]);
m[11] = 0.0f;
m[12] = 0.0f;
m[13] = 0.0f;
m[14] = 0.0f;
m[15] = 1.0f;
return m;
}
/* our own collectio of 3D vector functions */
public static void vzero(float[] v) {
v[0] = 0.0f;
v[1] = 0.0f;
v[2] = 0.0f;
}
public static void vset(float[] v, float x, float y, float z){
v[0] = x;
v[1] = y;
v[2] = z;
}
public static void vsub(float[] src1, float[] src2, float[] dst){
dst[0] = src1[0] - src2[0];
dst[1] = src1[1] - src2[1];
dst[2] = src1[2] - src2[2];
}
public static void vcopy(float[] v1, float[] v2){
for (int i = 0 ; i < 3 ; i++)
v2[i] = v1[i];
}
public static void vcross(float[] v1, float[] v2, float[] cross) {
float[] temp = new float[3];
temp[0] = (v1[1] * v2[2]) - (v1[2] * v2[1]);
temp[1] = (v1[2] * v2[0]) - (v1[0] * v2[2]);
temp[2] = (v1[0] * v2[1]) - (v1[1] * v2[0]);
vcopy(temp, cross);
}
public static float vlength(float[] v) {
return (float) Math.sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
}
public static void vscale(float[] v, float div) {
v[0] *= div;
v[1] *= div;
v[2] *= div;
}
public static void vnormal(float[] v) {
vscale(v,1.0f/vlength(v));
}
public static float vdot(float[] v1, float[] v2) {
return v1[0]*v2[0] + v1[1]*v2[1] + v1[2]*v2[2];
}
public static void vadd(float[] src1, float[] src2, float[] dst){
dst[0] = src1[0] + src2[0];
dst[1] = src1[1] + src2[1];
dst[2] = src1[2] + src2[2];
}
} |
