Initial commit.

physics/rotation.h

@@ -0,0 +1,79 @@
+// -*- C++ -*-
+
+#ifndef MBOSTOCK_ROTATION_H
+#define MBOSTOCK_ROTATION_H
+
+#include "shape.h"
+#include "vector.h"
+#include "transform.h"
+
+namespace mbostock {
+
+  /**
+   * Computes a rotation matrix for a given origin, axis and angle. This is
+   * roughly the equivalent to a glTranslatef and glRotatef call in OpenGL.
+   */
+  class Rotation : public Transform {
+  public:
+    Rotation(const Vector& origin, const Vector& axis,
+             float speed, float angle);
+
+    /** Rotates the specified point. */
+    Vector point(const Vector& x) const;
+
+    /** Inverse-rotates the specified point. */
+    Vector pointInverse(const Vector& x) const;
+
+    /** Rotates the specified vector. */
+    Vector vector(const Vector& x) const;
+
+    /** Inverse-rotates the specified vector. */
+    Vector vectorInverse(const Vector& x) const;
+
+    /** Returns the rotation's origin. */
+    inline const Vector& origin() const { return origin_; }
+
+    /** Returns the rotation's axis. */
+    inline const Vector& axis() const { return axis_; }
+
+    /** Returns the rotation's angle (in degrees, in the range [0, 360]). */
+    inline float angle() const { return angle_; }
+
+    /** Returns the speed of the rotation (in degrees per time step). */
+    inline float speed() const { return speed_; }
+
+    /** Advances the rotation by one time step. */
+    virtual void step();
+
+    /** Resets the rotation. */
+    virtual void reset();
+
+    /** Returns the velocity of the given point. */
+    Vector velocity(const Vector& x) const;
+
+  private:
+    void update();
+
+    Vector origin_;
+    Vector axis_;
+    float startAngle_;
+    float angle_;
+    float speed_;
+    float matrix_[9];
+  };
+
+  class RotatingShape : public Shape {
+  public:
+    RotatingShape(const Shape& s, const Rotation& r);
+
+    virtual bool intersects(const Sphere& s) const;
+    virtual Projection project(const Vector& x) const;
+
+  private:
+    const Shape& shape_;
+    const Rotation& rotation_;
+  };
+
+}
+
+#endif