diff --git a/src/r_draw.cpp b/src/r_draw.cpp
index 55353a0068..8cca132898 100644
--- a/src/r_draw.cpp
+++ b/src/r_draw.cpp
@@ -100,6 +100,8 @@ void (*R_DrawFogBoundary)(int x1, int x2, short *uclip, short *dclip);
 void (*R_MapTiltedPlane)(int y, int x1);
 void (*R_MapColoredPlane)(int y, int x1);
 void (*R_DrawParticle)(vissprite_t *);
+void (*R_SetupDrawSlab)(FColormap *base_colormap, float light, int shade);
+void (*R_DrawSlab)(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
 fixed_t (*tmvline1_add)();
 void (*tmvline4_add)();
 fixed_t (*tmvline1_addclamp)();
@@ -2306,6 +2308,9 @@ void R_InitColumnDrawers ()
 		R_MapColoredPlane			= R_MapColoredPlane_rgba;
 		R_DrawParticle				= R_DrawParticle_rgba;
 
+		R_SetupDrawSlab				= R_SetupDrawSlab_rgba;
+		R_DrawSlab					= R_DrawSlab_rgba;
+
 		tmvline1_add				= tmvline1_add_rgba;
 		tmvline4_add				= tmvline4_add_rgba;
 		tmvline1_addclamp			= tmvline1_addclamp_rgba;
@@ -2403,6 +2408,14 @@ void R_InitColumnDrawers ()
 		R_MapColoredPlane			= R_MapColoredPlane_C;
 		R_DrawParticle				= R_DrawParticle_C;
 
+#ifdef X86_ASM
+		R_SetupDrawSlab				= [](FColormap *colormap, float light, int shade) { R_SetupDrawSlabA(colormap->Maps + (GETPALOOKUP(light, shade) << COLORMAPSHIFT)); };
+		R_DrawSlab					= R_DrawSlabA;
+#else
+		R_SetupDrawSlab				= [](FColormap *colormap, float light, int shade) { R_SetupDrawSlabC(colormap->Maps + (GETPALOOKUP(light, shade) << COLORMAPSHIFT)); };
+		R_DrawSlab					= R_DrawSlabC;
+#endif
+
 		tmvline1_add				= tmvline1_add_C;
 		tmvline4_add				= tmvline4_add_C;
 		tmvline1_addclamp			= tmvline1_addclamp_C;
diff --git a/src/r_draw.h b/src/r_draw.h
index b662ddcee3..547a044ea3 100644
--- a/src/r_draw.h
+++ b/src/r_draw.h
@@ -286,16 +286,16 @@ void	R_FillColumnP_C (void);
 void	R_FillColumnHorizP_C (void);
 void	R_FillSpan_C (void);
 
-#ifdef X86_ASM
-#define R_SetupDrawSlab R_SetupDrawSlabA
-#define R_DrawSlab R_DrawSlabA
-#else
-#define R_SetupDrawSlab R_SetupDrawSlabC
-#define R_DrawSlab R_DrawSlabC
-#endif
+extern void(*R_SetupDrawSlab)(FColormap *base_colormap, float light, int shade);
+extern void(*R_DrawSlab)(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
 
-extern "C" void			   R_SetupDrawSlab(const BYTE *colormap);
-extern "C" void R_DrawSlab(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
+#ifdef X86_ASM
+extern "C" void R_SetupDrawSlabA(const BYTE *colormap);
+extern "C" void R_DrawSlabA(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
+#else
+extern "C" void R_SetupDrawSlabC(const BYTE *colormap);
+extern "C" void R_DrawSlabC(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
+#endif
 
 extern "C" int				ds_y;
 extern "C" int				ds_x1;
diff --git a/src/r_draw_rgba.cpp b/src/r_draw_rgba.cpp
index 57b32b28c6..9603a8b3eb 100644
--- a/src/r_draw_rgba.cpp
+++ b/src/r_draw_rgba.cpp
@@ -2303,6 +2303,123 @@ public:
 	}
 };
 
+class DrawSlabRGBACommand : public DrawerCommand
+{
+	int _dx;
+	fixed_t _v;
+	int _dy;
+	fixed_t _vi;
+	const BYTE *_vptr;
+	uint32_t *_p;
+	ShadeConstants _shade_constants;
+	const BYTE *_colormap;
+	fixed_t _light;
+	int _pitch;
+	int _start_y;
+
+public:
+	DrawSlabRGBACommand(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p, ShadeConstants shade_constants, const BYTE *colormap, fixed_t light)
+	{
+		_dx = dx;
+		_v = v;
+		_dy = dy;
+		_vi = vi;
+		_vptr = vptr;
+		_p = (uint32_t *)p;
+		_shade_constants = shade_constants;
+		_colormap = colormap;
+		_light = light;
+		_pitch = dc_pitch;
+		_start_y = static_cast<int>((p - dc_destorg) / (dc_pitch * 4));
+		assert(dx > 0);
+	}
+
+	void Execute(DrawerThread *thread) override
+	{
+		int dx = _dx;
+		fixed_t v = _v;
+		int dy = _dy;
+		fixed_t vi = _vi;
+		const BYTE *vptr = _vptr;
+		uint32_t *p = _p;
+		ShadeConstants shade_constants = _shade_constants;
+		const BYTE *colormap = _colormap;
+		uint32_t light = calc_light_multiplier(_light);
+		int pitch = _pitch;
+		int x;
+
+		dy = thread->count_for_thread(_start_y, dy);
+		p = thread->dest_for_thread(_start_y, pitch, p);
+		v += vi * thread->skipped_by_thread(_start_y);
+		vi *= thread->num_cores;
+		pitch *= thread->num_cores;
+
+		if (dx == 1)
+		{
+			while (dy > 0)
+			{
+				*p = shade_pal_index(colormap[vptr[v >> FRACBITS]], light, shade_constants);
+				p += pitch;
+				v += vi;
+				dy--;
+			}
+		}
+		else if (dx == 2)
+		{
+			while (dy > 0)
+			{
+				uint32_t color = shade_pal_index(colormap[vptr[v >> FRACBITS]], light, shade_constants);
+				p[0] = color;
+				p[1] = color;
+				p += pitch;
+				v += vi;
+				dy--;
+			}
+		}
+		else if (dx == 3)
+		{
+			while (dy > 0)
+			{
+				uint32_t color = shade_pal_index(colormap[vptr[v >> FRACBITS]], light, shade_constants);
+				p[0] = color;
+				p[1] = color;
+				p[2] = color;
+				p += pitch;
+				v += vi;
+				dy--;
+			}
+		}
+		else if (dx == 4)
+		{
+			while (dy > 0)
+			{
+				uint32_t color = shade_pal_index(colormap[vptr[v >> FRACBITS]], light, shade_constants);
+				p[0] = color;
+				p[1] = color;
+				p[2] = color;
+				p[3] = color;
+				p += pitch;
+				v += vi;
+				dy--;
+			}
+		}
+		else while (dy > 0)
+		{
+			uint32_t color = shade_pal_index(colormap[vptr[v >> FRACBITS]], light, shade_constants);
+			// The optimizer will probably turn this into a memset call.
+			// Since dx is not likely to be large, I'm not sure that's a good thing,
+			// hence the alternatives above.
+			for (x = 0; x < dx; x++)
+			{
+				p[x] = color;
+			}
+			p += pitch;
+			v += vi;
+			dy--;
+		}
+	}
+};
+
 class Vlinec1RGBACommand : public DrawerCommand
 {
 	DWORD _iscale;
@@ -3813,6 +3930,31 @@ void R_FillSpan_rgba()
 	DrawerCommandQueue::QueueCommand<FillSpanRGBACommand>();
 }
 
+static ShadeConstants slab_rgba_shade_constants;
+static const BYTE *slab_rgba_colormap;
+static fixed_t slab_rgba_light;
+
+void R_SetupDrawSlab_rgba(FColormap *base_colormap, float light, int shade)
+{
+	slab_rgba_shade_constants.light_red = base_colormap->Color.r * 256 / 255;
+	slab_rgba_shade_constants.light_green = base_colormap->Color.g * 256 / 255;
+	slab_rgba_shade_constants.light_blue = base_colormap->Color.b * 256 / 255;
+	slab_rgba_shade_constants.light_alpha = base_colormap->Color.a * 256 / 255;
+	slab_rgba_shade_constants.fade_red = base_colormap->Fade.r;
+	slab_rgba_shade_constants.fade_green = base_colormap->Fade.g;
+	slab_rgba_shade_constants.fade_blue = base_colormap->Fade.b;
+	slab_rgba_shade_constants.fade_alpha = base_colormap->Fade.a;
+	slab_rgba_shade_constants.desaturate = MIN(abs(base_colormap->Desaturate), 255) * 255 / 256;
+	slab_rgba_shade_constants.simple_shade = (base_colormap->Color.d == 0x00ffffff && base_colormap->Fade.d == 0x00000000 && base_colormap->Desaturate == 0);
+	slab_rgba_colormap = base_colormap->Maps;
+	slab_rgba_light = LIGHTSCALE(light, shade);
+}
+
+void R_DrawSlab_rgba(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p)
+{
+	DrawerCommandQueue::QueueCommand<DrawSlabRGBACommand>(dx, v, dy, vi, vptr, p, slab_rgba_shade_constants, slab_rgba_colormap, slab_rgba_light);
+}
+
 //extern FTexture *rw_pic; // For the asserts below
 
 DWORD vlinec1_rgba()
diff --git a/src/r_draw_rgba.h b/src/r_draw_rgba.h
index 617e831079..c94cb1e4b9 100644
--- a/src/r_draw_rgba.h
+++ b/src/r_draw_rgba.h
@@ -90,6 +90,9 @@ void R_DrawSpanAddClamp_rgba();
 void R_DrawSpanMaskedAddClamp_rgba();
 void R_FillSpan_rgba();
 
+void R_SetupDrawSlab_rgba(FColormap *base_colormap, float light, int shade);
+void R_DrawSlab_rgba(int dx, fixed_t v, int dy, fixed_t vi, const BYTE *vptr, BYTE *p);
+
 void R_DrawFogBoundary_rgba(int x1, int x2, short *uclip, short *dclip);
 
 DWORD vlinec1_rgba();
diff --git a/src/r_things.cpp b/src/r_things.cpp
index f6a1a709fc..e1f1017f36 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -688,7 +688,7 @@ void R_DrawVisVoxel(vissprite_t *spr, int minslabz, int maxslabz, short *cliptop
 
 	// Render the voxel, either directly to the screen or offscreen.
 	R_DrawVoxel(spr->pa.vpos, spr->pa.vang, spr->gpos, spr->Angle,
-		spr->xscale, FLOAT2FIXED(spr->yscale), spr->voxel, spr->Style.BaseColormap->Maps + (spr->Style.ColormapNum << COLORMAPSHIFT), cliptop, clipbot,
+		spr->xscale, FLOAT2FIXED(spr->yscale), spr->voxel, spr->Style.BaseColormap, spr->Style.ColormapNum, cliptop, clipbot,
 		minslabz, maxslabz, flags);
 
 	// Blend the voxel, if that's what we need to do.
@@ -2775,7 +2775,7 @@ extern double BaseYaspectMul;;
 void R_DrawVoxel(const FVector3 &globalpos, FAngle viewangle,
 	const FVector3 &dasprpos, DAngle dasprang,
 	fixed_t daxscale, fixed_t dayscale, FVoxel *voxobj,
-	lighttable_t *colormap, short *daumost, short *dadmost, int minslabz, int maxslabz, int flags)
+	FColormap *colormap, int colormapnum, short *daumost, short *dadmost, int minslabz, int maxslabz, int flags)
 {
 	int i, j, k, x, y, syoff, ggxstart, ggystart, nxoff;
 	fixed_t cosang, sinang, sprcosang, sprsinang;
@@ -2812,7 +2812,7 @@ void R_DrawVoxel(const FVector3 &globalpos, FAngle viewangle,
 	sprcosang = FLOAT2FIXED(dasprang.Cos()) >> 2;
 	sprsinang = FLOAT2FIXED(-dasprang.Sin()) >> 2;
 
-	R_SetupDrawSlab(colormap);
+	R_SetupDrawSlab(colormap, 0.0f, colormapnum << FRACBITS);
 
 	int pixelsize = r_swtruecolor ? 4 : 1;
 
diff --git a/src/r_things.h b/src/r_things.h
index 04d5487ee1..13f89574b5 100644
--- a/src/r_things.h
+++ b/src/r_things.h
@@ -144,7 +144,7 @@ enum { DVF_OFFSCREEN = 1, DVF_SPANSONLY = 2, DVF_MIRRORED = 4 };
 void R_DrawVoxel(const FVector3 &viewpos, FAngle viewangle,
 	const FVector3 &sprpos, DAngle dasprang,
 	fixed_t daxscale, fixed_t dayscale, struct FVoxel *voxobj,
-	lighttable_t *colormap, short *daumost, short *dadmost, int minslabz, int maxslabz, int flags);
+	FColormap *colormap, int colormapnum, short *daumost, short *dadmost, int minslabz, int maxslabz, int flags);
 
 void R_ClipVisSprite (vissprite_t *vis, int xl, int xh);