diff --git a/glslUtil/glslUtil.c b/glslUtil/glslUtil.c
index f7b716d..f681c15 100644
--- a/glslUtil/glslUtil.c
+++ b/glslUtil/glslUtil.c
@@ -1,4 +1,5 @@
 
+#include <math.h>
 #include <string.h>
 #include "glslUtil.h"
 
@@ -58,6 +59,41 @@ void guMatrixScale(guMatrix4x4 *m, GLfloat x, GLfloat y, GLfloat z)
     }
 }
 
+void guMatrixRotate(guMatrix4x4 *m, GLfloat angle,
+        GLfloat x, GLfloat y, GLfloat z)
+{
+    GLfloat lx = x, ly = y, lz = z, p;
+    p = lx*lx + ly*ly + lz*lz;
+    if (p != 1.0)
+    {
+        GLfloat scale = sqrt(p);
+        lx /= scale;
+        ly /= scale;
+        lz /= scale;
+    }
+    GLfloat c = cos(angle);
+    GLfloat s = sin(angle);
+    guMatrix4x4 mult;
+    GLfloat oc = 1 - c;
+    mult[0][0] = lx * lx * oc + c;
+    mult[0][1] = lx * ly * oc - lz * s;
+    mult[0][2] = lx * lz * oc + ly * s;
+    mult[0][3] = 0.0;
+    mult[1][0] = ly * lx * oc + lz * s;
+    mult[1][1] = ly * ly * oc + c;
+    mult[1][2] = ly * lz * oc - lx * s;
+    mult[1][3] = 0.0;
+    mult[2][0] = lx * lz * oc - ly * s;
+    mult[2][1] = ly * lz * oc + lx * s;
+    mult[2][2] = lz * lz * oc + c;
+    mult[2][3] = 0.0;
+    mult[3][0] = 0.0;
+    mult[3][1] = 0.0;
+    mult[3][2] = 0.0;
+    mult[3][3] = 1.0;
+    guMatrixMult(m, m, &mult);
+}
+
 void guMatrixFrustum(guMatrix4x4 *m,
         GLfloat left, GLfloat right,
         GLfloat bottom, GLfloat top,
diff --git a/glslUtil/glslUtil.h b/glslUtil/glslUtil.h
index 1d961d2..ec03737 100644
--- a/glslUtil/glslUtil.h
+++ b/glslUtil/glslUtil.h
@@ -18,6 +18,8 @@ void guMatrixLoadIdentity(guMatrix4x4 *m);
 void guMatrixMult(guMatrix4x4 *m, guMatrix4x4 *a, guMatrix4x4 *b);
 void guMatrixTranslate(guMatrix4x4 *m, GLfloat x, GLfloat y, GLfloat z);
 void guMatrixScale(guMatrix4x4 *m, GLfloat x, GLfloat y, GLfloat z);
+void guMatrixRotate(guMatrix4x4 *m, GLfloat angle,
+        GLfloat x, GLfloat y, GLfloat z);
 void guMatrixFrustum(guMatrix4x4 *m,
         GLfloat left, GLfloat right,
         GLfloat bottom, GLfloat top,