diff --git a/ss/LightBounce.cc b/ss/LightBounce.cc
index 26e4e6b..c6071d4 100644
--- a/ss/LightBounce.cc
+++ b/ss/LightBounce.cc
@@ -44,6 +44,14 @@ LightBounceBox::~LightBounceBox()
     glDeleteLists(m_dl, 1);
 }
 
+void LightBounceBox::updateDist(float x, float y, float z)
+{
+    float dx = x - this->x;
+    float dy = y - this->y;
+    float dz = z - this->z;
+    this->dist = (dx*dx) + (dy*dy) + (dz*dz);
+}
+
 /* construct screensaver mode and do some basic OpenGL setup */
 LightBounce::LightBounce(SSMain * _SSMain) : SSMode(_SSMain)
 {
diff --git a/ss/LightBounce.h b/ss/LightBounce.h
index 664dbdf..35dd995 100644
--- a/ss/LightBounce.h
+++ b/ss/LightBounce.h
@@ -20,7 +20,7 @@ public:
                    float xr, float yr, float zr);
     ~LightBounceBox();
     void draw() { glCallList(m_dl); }
-    float dist;
+    void updateDist(float x, float y, float z);
 
 private:
     float x;
@@ -29,6 +29,7 @@ private:
     float xr;
     float yr;
     float zr;
+    float dist;
 
     GLuint m_dl;
 };