diff --git a/src/lua_mobjlib.c b/src/lua_mobjlib.c
index 91c2158e8..22cb0f00a 100644
--- a/src/lua_mobjlib.c
+++ b/src/lua_mobjlib.c
@@ -16,6 +16,7 @@
 #ifdef HAVE_BLUA
 #include "fastcmp.h"
 #include "r_things.h"
+#include "r_main.h"
 #include "p_local.h"
 #include "g_game.h"
 #include "p_setup.h"
@@ -65,6 +66,8 @@ int mobj_mobjnum_unimplemented(lua_State *L);
 int mobj_scale_setter(lua_State *L);
 int mobj_destscale_setter(lua_State *L);
 int mobj_standingslope_noset(lua_State *L);
+int mobj_rollsum_getter(lua_State *L);
+int mobj_rollsum_noset(lua_State *L);
 
 static const char *const array_opt[] ={"iterate",NULL};
 
@@ -78,6 +81,8 @@ static const udata_field_t mobj_fields[] = {
     FIELD(mobj_t, angle,               udatalib_getter_angle,      mobj_angle_setter),
     FIELD(mobj_t, rollangle,           udatalib_getter_angle,      udatalib_setter_angle),
     FIELD(mobj_t, sloperoll,           udatalib_getter_angle,      mobj_sloperoll_noop),
+	// Macro fails here
+	{ "rollsum", 0, mobj_rollsum_getter, mobj_rollsum_noset },
     FIELD(mobj_t, sprite,              udatalib_getter_spritenum,  udatalib_setter_spritenum),
     FIELD(mobj_t, frame,               udatalib_getter_uint32,     udatalib_setter_uint32),
     FIELD(mobj_t, anim_duration,       udatalib_getter_uint16,     udatalib_setter_uint16),
@@ -174,13 +179,21 @@ int mobj_ ## field ## _noset(lua_State *L) \
     return luaL_error(L, LUA_QL("mobj_t") " field " LUA_QS " should not be set directly.", #field); \
 }
 
+#define NOSET_USE(field, use) \
+int mobj_ ## field ## _noset(lua_State *L) \
+{ \
+    return luaL_error(L, LUA_QL("mobj_t") " field " LUA_QS " should not be set directly. Use " LUA_QL(use) " instead.", #field); \
+}
+
 NOSET(snext)
 NOSET(bnext)
 NOSET(info)
 NOSET(player)
 NOSET(standingslope)
+NOSET_USE(rollsum, "rollangle")
 
 #undef NOSET
+#undef NOSET_USE
 
 // Unimplemented fields (why would you need to set them like that explicitly?
 // No idea, i'm keeping it for synch reasons)
@@ -539,6 +552,24 @@ int mobj_destscale_setter(lua_State *L)
     return 0;
 }
 
+// WARNING: Not synch safe!
+// Don't use this field in game logic code!
+int mobj_rollsum_getter(lua_State *L)
+{
+	mobj_t *mo = GETMO();
+
+	angle_t rollsum = mo->rollangle + cv_sloperoll.value ? mo->sloperoll : 0;
+
+	if (mo->player)
+	{
+		rollsum += R_PlayerSliptideAngle(mo->player);
+	}
+
+	lua_pushangle(L, rollsum);
+
+	return 1;
+}
+
 static int mobj_get(lua_State *L)
 {
 	mobj_t *mo = *((mobj_t **)luaL_checkudata(L, 1, META_MOBJ));
diff --git a/src/lua_playerlib.c b/src/lua_playerlib.c
index c687921ec..8ce7840f3 100644
--- a/src/lua_playerlib.c
+++ b/src/lua_playerlib.c
@@ -13,6 +13,7 @@
 #include "doomdef.h"
 #ifdef HAVE_BLUA
 #include "fastcmp.h"
+#include "r_main.h"
 #include "p_mobj.h"
 #include "d_player.h"
 #include "g_game.h"
@@ -44,6 +45,10 @@ int player_splitscreenindex_noset(lua_State *L);
 int player_ping_getter(lua_State *L);
 int player_ping_noset(lua_State *L);
 
+// Non synch safe!
+int player_sliproll_getter(lua_State *L);
+int player_sliproll_noset(lua_State *L);
+
 #define FIELD(type, field_name, getter, setter) { #field_name, offsetof(type, field_name), getter, setter }
 static const udata_field_t player_fields[] = {
     // Player doesn't actually have field "name" so macro fails. Need to declare field manually.
@@ -150,6 +155,7 @@ static const udata_field_t player_fields[] = {
     FIELD(player_t, fovadd,           udatalib_getter_fixed,       udatalib_setter_fixed), // Mmm yeah thats definitely synch safe
 #endif
     // Same as player.name
+	{ "sliproll", 0, player_sliproll_getter, player_sliproll_noset },
     { "ping", 0, player_ping_getter, player_ping_noset }, // Hmm originally setter doesn't exist so data is written as unreachable custom field...
     { NULL },
 };
@@ -207,6 +213,7 @@ NOSET(kartstuff)
 NOSET(bot)
 NOSET(splitscreenindex)
 NOSET(ping)
+NOSET(sliproll)
 
 #undef NOSET
 
@@ -331,6 +338,15 @@ int player_ping_getter(lua_State *L)
     return 1;
 }
 
+int player_sliproll_getter(lua_State *L)
+{
+	player_t *plr = GETPLAYER();
+
+	lua_pushangle(L, R_PlayerSliptideAngle(plr));
+
+	return 1;
+}
+
 static int lib_iteratePlayers(lua_State *L)
 {
 	INT32 i = -1;
diff --git a/src/r_defs.h b/src/r_defs.h
index 559e3646b..26a11a6c0 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -19,6 +19,7 @@
 
 // We rely on the thinker data struct to handle sound origins in sectors.
 #include "d_think.h"
+
 // SECTORS do store MObjs anyway.
 #include "p_mobj.h"
 
diff --git a/src/r_main.c b/src/r_main.c
index dc914e79a..c381c9860 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -439,6 +439,60 @@ fixed_t R_PointToDist2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1)
 	return FixedHypot(px1 - px2, py1 - py2);
 }
 
+angle_t R_PlayerSliptideAngle(player_t *player)
+{
+	mobj_t *mo = player->mo;
+
+	if (!cv_sliptideroll.value || !mo || P_MobjWasRemoved(mo)) return 0;
+
+	size_t rot = mo->frame&FF_FRAMEMASK;
+	boolean papersprite = (mo->frame & FF_PAPERSPRITE);
+
+	spritedef_t *sprdef;
+	spriteframe_t *sprframe;
+	angle_t ang = 0;
+
+	interpmobjstate_t interp = {0};
+
+	// Yes.
+	if (R_UsingFrameInterpolation() && !paused)
+	{
+		R_InterpolateMobjState(mo, rendertimefrac, &interp);
+	}
+	else
+	{
+		R_InterpolateMobjState(mo, FRACUNIT, &interp);
+	}
+
+	if (mo->skin && mo->sprite == SPR_PLAY)
+	{
+		sprdef = &((skin_t *)mo->skin)->spritedef;
+
+		if (rot >= sprdef->numframes)
+			sprdef = &sprites[mo->sprite];
+	}
+	else
+	{
+		sprdef = &sprites[mo->sprite];
+	}
+
+	if (rot >= sprdef->numframes)
+	{
+		sprdef = &sprites[states[S_UNKNOWN].sprite];
+		rot = states[S_UNKNOWN].frame&FF_FRAMEMASK;
+	}
+
+	sprframe = &sprdef->spriteframes[rot];
+
+	// No sprite frame? I guess it is possible
+	if (!sprframe) return 0;
+
+	if (sprframe->rotate != SRF_SINGLE || papersprite)
+		ang = R_PointToAngle(interp.x, interp.y) - interp.angle;
+
+	return FixedMul(FINECOSINE((ang) >> ANGLETOFINESHIFT), mo->player->sliproll*(mo->player->sliptidemem));
+}
+
 // Little extra utility. Works in the same way as R_PointToAngle2
 fixed_t R_PointToDist(fixed_t x, fixed_t y)
 {
diff --git a/src/r_main.h b/src/r_main.h
index 70adf1bb5..d6c966857 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -73,6 +73,7 @@ angle_t R_PointToAngle2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
 angle_t R_PointToAngleEx(INT32 x2, INT32 y2, INT32 x1, INT32 y1);
 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);
+angle_t R_PlayerSliptideAngle(player_t *player);
 
 fixed_t R_ScaleFromGlobalAngle(angle_t visangle);
 subsector_t *R_PointInSubsector(fixed_t x, fixed_t y);