diff --git a/src/m_fixed.h b/src/m_fixed.h
index 70402f27..34fd25db 100644
--- a/src/m_fixed.h
+++ b/src/m_fixed.h
@@ -46,41 +46,6 @@ typedef INT32 fixed_t;
 #define FLOAT_TO_FIXED(f) (fixed_t)((f) * ((float)FRACUNIT))
 
 
-/**	\brief	The TMulScale16 function
-
-	\param	a	a parameter of type fixed_t
-	\param	b	a parameter of type fixed_t
-	\param	c	a parameter of type fixed_t
-	\param	d	a parameter of type fixed_t
-	\param	e	a parameter of type fixed_t
-	\param	f	a parameter of type fixed_t
-
-	\return	fixed_t
-
-
-*/
-FUNCMATH FUNCINLINE static ATTRINLINE fixed_t TMulScale16(fixed_t a, fixed_t b, fixed_t c, fixed_t d, fixed_t e, fixed_t f) \
-{ \
-	return (fixed_t)((((INT64)a * (INT64)b) + ((INT64)c * (INT64)d) \
-		+ ((INT64)e * (INT64)f)) >> 16); \
-}
-
-/**	\brief	The DMulScale16 function
-
-	\param	a	a parameter of type fixed_t
-	\param	b	a parameter of type fixed_t
-	\param	c	a parameter of type fixed_t
-	\param	d	a parameter of type fixed_t
-
-	\return	fixed_t
-
-
-*/
-FUNCMATH FUNCINLINE static ATTRINLINE fixed_t DMulScale16(fixed_t a, fixed_t b, fixed_t c, fixed_t d) \
-{ \
-	return (fixed_t)((((INT64)a * (INT64)b) + ((INT64)c * (INT64)d)) >> 16); \
-}
-
 #if defined (__WATCOMC__) && FRACBITS == 16
 	#pragma aux FixedMul =  \
 		"imul ebx",         \
diff --git a/src/r_defs.h b/src/r_defs.h
index 2c5860ee..3669ec8f 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -224,15 +224,6 @@ typedef struct linechain_s
 
 
 
-// ZDoom C++ to Legacy C conversion Tails 04-29-2002 (for slopes)
-typedef struct secplane_t
-{
-	// the plane is defined as a*x + b*y + c*z + d = 0
-	// ic is 1/c, for faster Z calculations
-
-	fixed_t a, b, c, d, ic;
-} secplane_t;
-
 // Slopes
 #ifdef ESLOPE
 typedef enum {
diff --git a/src/r_main.c b/src/r_main.c
index 498f4dab..e1fe0dce 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -366,69 +366,6 @@ fixed_t R_PointToDist(fixed_t x, fixed_t y)
 	return R_PointToDist2(viewx, viewy, x, y);
 }
 
-/***************************************
-*** Zdoom C++ to Legacy C conversion ***
-****************************************/
-
-// Utility to find the Z height at an XY location in a sector (for slopes)
-fixed_t R_SecplaneZatPoint(secplane_t *secplane, fixed_t x, fixed_t y)
-{
-	return FixedMul(secplane->ic, -secplane->d - DMulScale16(secplane->a, x, secplane->b, y));
-}
-
-// Returns the value of z at (x,y) if d is equal to dist
-fixed_t R_SecplaneZatPointDist (secplane_t *secplane, fixed_t x, fixed_t y, fixed_t dist)
-{
-	return FixedMul(secplane->ic, -dist - DMulScale16(secplane->a, x, secplane->b, y));
-}
-
-// Flips the plane's vertical orientiation, so that if it pointed up,
-// it will point down, and vice versa.
-void R_SecplaneFlipVert(secplane_t *secplane)
-{
-	secplane->a = -secplane->a;
-	secplane->b = -secplane->b;
-	secplane->c = -secplane->c;
-	secplane->d = -secplane->d;
-	secplane->ic = -secplane->ic;
-}
-
-// Returns true if 2 planes are the same
-boolean R_ArePlanesSame(secplane_t *original, secplane_t *other)
-{
-	return original->a == other->a && original->b == other->b
-		&& original->c == other->c && original->d == other->d;
-}
-
-// Returns true if 2 planes are different
-boolean R_ArePlanesDifferent(secplane_t *original, secplane_t *other)
-{
-	return original->a != other->a || original->b != other->b
-		|| original->c != other->c || original->d != other->d;
-}
-
-// Moves a plane up/down by hdiff units
-void R_SecplaneChangeHeight(secplane_t *secplane, fixed_t hdiff)
-{
-	secplane->d = secplane->d - FixedMul(hdiff, secplane->c);
-}
-
-// Returns how much this plane's height would change if d were set to oldd
-fixed_t R_SecplaneHeightDiff(secplane_t *secplane, fixed_t oldd)
-{
-	return FixedMul(oldd - secplane->d, secplane->ic);
-}
-
-fixed_t R_SecplanePointToDist(secplane_t *secplane, fixed_t x, fixed_t y, fixed_t z)
-{
-	return -TMulScale16(secplane->a, x, y, secplane->b, z, secplane->c);
-}
-
-fixed_t R_SecplanePointToDist2(secplane_t *secplane, fixed_t x, fixed_t y, fixed_t z)
-{
-	return -TMulScale16(secplane->a, x, secplane->b, y, z, secplane->c);
-}
-
 //
 // R_ScaleFromGlobalAngle
 // Returns the texture mapping scale for the current line (horizontal span)
diff --git a/src/r_main.h b/src/r_main.h
index 8f46a938..2e768cb9 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -61,18 +61,6 @@ angle_t R_PointToAngle2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
 fixed_t R_PointToDist(fixed_t x, fixed_t y);
 fixed_t R_PointToDist2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
 
-// ZDoom C++ to Legacy C conversion Tails 04-29-2002
-fixed_t R_SecplaneZatPoint(secplane_t *secplane, fixed_t x, fixed_t y);
-fixed_t R_SecplaneZatPointDist(secplane_t *secplane, fixed_t x, fixed_t y,
-	fixed_t dist);
-void R_SecplaneFlipVert(secplane_t *secplane);
-boolean R_ArePlanesSame(secplane_t *original,  secplane_t *other);
-boolean R_ArePlanesDifferent(secplane_t *original,  secplane_t *other);
-void R_SecplaneChangeHeight(secplane_t *secplane, fixed_t hdiff);
-fixed_t R_SecplaneHeightDiff(secplane_t *secplane, fixed_t oldd);
-fixed_t R_SecplanePointToDist(secplane_t *secplane, fixed_t x, fixed_t y, fixed_t z);
-fixed_t R_SecplanePointToDist2(secplane_t *secplane, fixed_t x, fixed_t y, fixed_t z);
-
 fixed_t R_ScaleFromGlobalAngle(angle_t visangle);
 subsector_t *R_PointInSubsector(fixed_t x, fixed_t y);
 subsector_t *R_IsPointInSubsector(fixed_t x, fixed_t y);