Initial commit.

ball.cpp

@@ -0,0 +1,26 @@
+// -*- C++ -*-
+
+#include "ball.h"
+#include "material.h"
+#include "model.h"
+#include "physics/shape.h"
+#include "physics/vector.h"
+#include "room.h"
+
+using namespace mbostock;
+
+Ball::Ball(const Vector& x, float radius)
+    : sphere_(x, radius), model_(sphere_) {
+}
+
+Model& Ball::model() {
+  return model_;
+}
+
+const Shape& Ball::shape() const {
+  return sphere_;
+}
+
+float Ball::slip() const {
+  return model_.material().slip();
+}