source: trunk/src/testing/app/volvis/Trackball.h @ 4

#ifndef Trackball_H
#define Trackball_H

class  Trackball {
  
 public:
  Trackball();
  ~Trackball();

  void start(float x, float y);

  // Pass the x and y coordinates of the last and current positions of
  // the mouse, scaled so they are from (-1.0 ... 1.0).
  //
  // The resulting rotation is returned as a quaternion rotation in the
  // first paramater.
  void update(float x, float y);

  // This function was added by joe kniss to facilitate a home key!
  void clear();

  // A useful function, builds a rotation matrix in Matrix based on
  // given quaternion.
  void buildRotMatrix(float m[4][4]);

  // This function computes a quaternion based on an axis (defined by
  // the given vector) and an angle about which to rotate.  The angle is
  // expressed in radians.  The result is put into the third argument.
  void reapply();

  // This funciton was also written by joe to allow arbitary views
  void setMatrix(float rot[16]);
  void getAxisAngle(float& angle, float axis[3]);

 private:
  static float        trackballSize;
  static int          renormCount;

  float               curQuat[4];
  float               lastQuat[4];
  float               lastX;
  float               lastY;
  float         a[3]; /* Axis of rotation */
  float         phi;  /* how much to rotate about axis */

  float projectToSphere(float, float, float);

};

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#endif