diff --git a/dtool/src/dtoolbase/cmath.I b/dtool/src/dtoolbase/cmath.I
index ddb552961e..030eca6a33 100644
--- a/dtool/src/dtoolbase/cmath.I
+++ b/dtool/src/dtoolbase/cmath.I
@@ -190,6 +190,15 @@ cceil(double f) {
   #endif
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: cfrac
+//  Description: Returns the fractional component of f: f - cfloor(f).
+////////////////////////////////////////////////////////////////////
+INLINE double
+cfrac(double f) {
+  return f - cfloor(f);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: csqrt
 //  Description: 
diff --git a/dtool/src/dtoolbase/cmath.h b/dtool/src/dtoolbase/cmath.h
index 53485d72fb..50103c7732 100644
--- a/dtool/src/dtoolbase/cmath.h
+++ b/dtool/src/dtoolbase/cmath.h
@@ -46,6 +46,7 @@ INLINE float cmod(float x, float y);
 
 INLINE double cfloor(double f);
 INLINE double cceil(double f);
+INLINE double cfrac(double f);
 INLINE double csqrt(double v);
 INLINE double csin(double v);
 INLINE double ccos(double v);