Initial commit.

physics/constraint.h

@@ -0,0 +1,125 @@
+// -*- C++ -*-
+
+#ifndef MBOSTOCK_CONSTRAINT_H
+#define MBOSTOCK_CONSTRAINT_H
+
+#include "shape.h"
+#include "vector.h"
+
+namespace mbostock {
+
+  class Particle;
+  class Shape;
+
+  class Constraints {
+  public:
+
+    /**
+     * Constrains a particle a to be distance d from position p, independent of
+     * mass.
+     */
+    static bool distance(Particle& a, Vector p, float d);
+
+    /**
+     * Constrains two particles a and b to be distance d apart. The particles
+     * are moved in opposite directions according to their relative mass, either
+     * towards or away from each other, depending on whether their actual
+     * distance is greater or less than the specified distance d.
+     */
+    static bool distance(Particle& a, Particle& b, float d);
+
+    /**
+     * Constrains a particle a to be at least distance d from position p,
+     * independent of mass.
+     */
+    static bool minDistance(Particle& a, Vector p, float d);
+
+    /**
+     * Constrains two particles a and b to be at least distance d apart. The
+     * particles are moved in opposite directions according to their relative
+     * mass, away from each other, if their actual distance is less than the
+     * specified distance d.
+     */
+    static bool minDistance(Particle& a, Particle& b, float d);
+
+    /**
+     * Constrains a particle a to be at most distance d from position p,
+     * independent of mass.
+     */
+    static bool maxDistance(Particle& a, Vector p, float d);
+
+    /**
+     * Constrains two particles a and b to be at most distance d apart. The
+     * particles are moved in opposite directions according to their relative
+     * mass, towards each other, if their actual distance is greater than the
+     * specified distance d.
+     */
+    static bool maxDistance(Particle& a, Particle& b, float d);
+
+    /**
+     * Constrains the particle so that its y-value is at least min. This
+     * implicitly uses a coefficient of restitution of zero.
+     */
+    static bool minY(Particle& a, float min) {
+      return plane(a, Vector(0, min, 0), Vector(0, 1, 0));
+    }
+
+    /**
+     * Constrains the particle so that its y-value is at least min, simulating a
+     * collision with a plane of coefficient of restitution kr. Note that the
+     * bounce can only be simulated if the particle was previously above the
+     * plane.
+     */
+    static bool minY(Particle& a, float min, float kr) {
+      return plane(a, Vector(0, min, 0), Vector(0, 1, 0), kr);
+    }
+
+    /**
+     * Constrains the particle to be above the plane defined by the point p and
+     * the normal n. This implicitly uses a coefficient of restitution of zero.
+     */
+    static bool plane(Particle& a, Vector p, Vector n);
+
+    /**
+     * Constrains the particle to be above the plane defined by the point p and
+     * the normal n, using a coefficient of restitution kr.
+     */
+    static bool plane(Particle& a, Vector p, Vector n, float kr);
+
+    /**
+     * Constrains the particle to be inside the specified shape by at least
+     * radius r. This implicitly uses a coefficient of restitution of zero.
+     */
+    static bool inside(Particle& a, const Shape& s, float r);
+
+    /**
+     * Constrains the particle to be inside the specified shape by at least
+     * radius r, using a coefficient of restitution kr.
+     */
+    static bool inside(Particle& a, const Shape& s, float r, float kr);
+
+    /**
+     * Constrains the particle to be outside the specified shape by at least
+     * radius r. This implicitly uses a coefficient of restitution of zero.
+     */
+    static bool outside(Particle& a, const Shape& s, float r);
+
+    /**
+     * Constrains the particle to be outside the specified shape by at least
+     * radius r, using a coefficient of restitution kr.
+     */
+    static bool outside(Particle& a, const Shape& s, float r, float kr);
+
+    /**
+     * Returns the projection information for the last call to a shape-based
+     * constraint.
+     */
+    static const Projection& projection();
+
+  private:
+    Constraints();
+  };
+
+}
+
+#endif