Initial commit.

trail.cpp

@@ -0,0 +1,38 @@
+// -*- C++ -*-
+
+#include "trail.h"
+
+using namespace mbostock;
+
+static const float minsq = .1f * .1f;
+
+Trail::Trail(const Vector& origin) {
+  points_.push_back(origin);
+}
+
+bool Trail::add(const Vector& p) {
+  if ((points_.back() - p).squared() >= minsq) {
+    points_.push_back(p);
+    return true;
+  }
+  return false;
+}
+
+TrailModel::TrailModel(const Trail& trail)
+    : trail_(trail) {
+}
+
+void TrailModel::display() {
+  glDisable(GL_LIGHTING);
+  glEnable(GL_BLEND);
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+  glColor4f(.6f, .2f, .3f, .5f);
+  glBegin(GL_LINE_STRIP);
+  std::vector<Vector>::const_iterator i;
+  for (i = trail_.points().begin(); i != trail_.points().end(); i++) {
+    glVertexv(*i);
+  }
+  glEnd();
+  glDisable(GL_BLEND);
+  glEnable(GL_LIGHTING);
+}