diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 46a42a92c..0602de9de 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -350,6 +350,7 @@ if(${SRB2_CONFIG_HWRENDER})
 	set(SRB2_HWRENDER_SOURCES
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_bsp.c
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_cache.c
+		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_clip.c
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_draw.c
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_light.c
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_main.c
@@ -358,6 +359,7 @@ if(${SRB2_CONFIG_HWRENDER})
 	)
 
 	set (SRB2_HWRENDER_HEADERS
+		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_clip.h
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_data.h
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_defs.h
 		${CMAKE_CURRENT_SOURCE_DIR}/hardware/hw_dll.h
diff --git a/src/Makefile b/src/Makefile
index 7a67c3f02..b159de3b8 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -269,7 +269,7 @@ ifndef DC
 endif
 	OPTS+=-DHWRENDER
 	OBJS+=$(OBJDIR)/hw_bsp.o $(OBJDIR)/hw_draw.o $(OBJDIR)/hw_light.o \
-		 $(OBJDIR)/hw_main.o $(OBJDIR)/hw_md2.o $(OBJDIR)/hw_cache.o $(OBJDIR)/hw_trick.o
+		 $(OBJDIR)/hw_main.o $(OBJDIR)/hw_clip.o $(OBJDIR)/hw_md2.o $(OBJDIR)/hw_cache.o $(OBJDIR)/hw_trick.o
 endif
 
 ifdef NOHS
@@ -719,7 +719,7 @@ ifdef MINGW
 $(OBJDIR)/r_opengl.o: hardware/r_opengl/r_opengl.c hardware/r_opengl/r_opengl.h \
  doomdef.h doomtype.h g_state.h m_swap.h hardware/hw_drv.h screen.h \
  command.h hardware/hw_data.h hardware/hw_glide.h hardware/hw_defs.h \
- hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h am_map.h \
+ hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h hardware/hw_clip.h am_map.h \
  d_event.h d_player.h p_pspr.h m_fixed.h tables.h info.h d_think.h \
  p_mobj.h doomdata.h d_ticcmd.h r_defs.h hardware/hw_dll.h
 	$(CC) $(CFLAGS) $(WFLAGS) -c $< -o $@
@@ -727,7 +727,7 @@ else
 $(OBJDIR)/r_opengl.o: hardware/r_opengl/r_opengl.c hardware/r_opengl/r_opengl.h \
  doomdef.h doomtype.h g_state.h m_swap.h hardware/hw_drv.h screen.h \
  command.h hardware/hw_data.h hardware/hw_glide.h hardware/hw_defs.h \
- hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h am_map.h \
+ hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h hardware/hw_clip.h am_map.h \
  d_event.h d_player.h p_pspr.h m_fixed.h tables.h info.h d_think.h \
  p_mobj.h doomdata.h d_ticcmd.h r_defs.h hardware/hw_dll.h
 	$(CC) $(CFLAGS) $(WFLAGS) -I/usr/X11R6/include -c $< -o $@
@@ -880,7 +880,7 @@ ifndef NOHW
 $(OBJDIR)/r_opengl.o: hardware/r_opengl/r_opengl.c hardware/r_opengl/r_opengl.h \
  doomdef.h doomtype.h g_state.h m_swap.h hardware/hw_drv.h screen.h \
  command.h hardware/hw_data.h hardware/hw_glide.h hardware/hw_defs.h \
- hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h am_map.h \
+ hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h hardware/hw_clip.h am_map.h \
  d_event.h d_player.h p_pspr.h m_fixed.h tables.h info.h d_think.h \
  p_mobj.h doomdata.h d_ticcmd.h r_defs.h hardware/hw_dll.h
 	$(CC) $(CFLAGS) $(WFLAGS) -D_WINDOWS -mwindows -c $< -o $@
@@ -888,7 +888,7 @@ $(OBJDIR)/r_opengl.o: hardware/r_opengl/r_opengl.c hardware/r_opengl/r_opengl.h
 $(OBJDIR)/ogl_win.o: hardware/r_opengl/ogl_win.c hardware/r_opengl/r_opengl.h \
  doomdef.h doomtype.h g_state.h m_swap.h hardware/hw_drv.h screen.h \
  command.h hardware/hw_data.h hardware/hw_glide.h hardware/hw_defs.h \
- hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h am_map.h \
+ hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h hardware/hw_clip.h am_map.h \
  d_event.h d_player.h p_pspr.h m_fixed.h tables.h info.h d_think.h \
  p_mobj.h doomdata.h d_ticcmd.h r_defs.h hardware/hw_dll.h
 	$(CC) $(CFLAGS) $(WFLAGS) -D_WINDOWS -mwindows -c $< -o $@
@@ -896,7 +896,7 @@ $(OBJDIR)/ogl_win.o: hardware/r_opengl/ogl_win.c hardware/r_opengl/r_opengl.h \
 $(OBJDIR)/r_minigl.o: hardware/r_minigl/r_minigl.c hardware/r_opengl/r_opengl.h \
  doomdef.h doomtype.h g_state.h m_swap.h hardware/hw_drv.h screen.h \
  command.h hardware/hw_data.h hardware/hw_glide.h hardware/hw_defs.h \
- hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h am_map.h \
+ hardware/hw_md2.h hardware/hw_glob.h hardware/hw_main.h hardware/hw_clip.h am_map.h \
  d_event.h d_player.h p_pspr.h m_fixed.h tables.h info.h d_think.h \
  p_mobj.h doomdata.h d_ticcmd.h r_defs.h hardware/hw_dll.h
 	$(CC) $(CFLAGS) $(WFLAGS) -D_WINDOWS -mwindows -c $< -o $@
diff --git a/src/hardware/hw_clip.c b/src/hardware/hw_clip.c
new file mode 100644
index 000000000..47cbbfa2b
--- /dev/null
+++ b/src/hardware/hw_clip.c
@@ -0,0 +1,465 @@
+/* Emacs style mode select   -*- C++ -*-
+ *-----------------------------------------------------------------------------
+ *
+ *
+ *  PrBoom: a Doom port merged with LxDoom and LSDLDoom
+ *  based on BOOM, a modified and improved DOOM engine
+ *  Copyright (C) 1999 by
+ *  id Software, Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
+ *  Copyright (C) 1999-2000 by
+ *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
+ *  Copyright 2005, 2006 by
+ *  Florian Schulze, Colin Phipps, Neil Stevens, Andrey Budko
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version 2
+ *  of the License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ *  02111-1307, USA.
+ *
+ * DESCRIPTION:
+ *
+ *---------------------------------------------------------------------
+ */
+
+/*
+ *
+ ** gl_clipper.cpp
+ **
+ ** Handles visibility checks.
+ ** Loosely based on the JDoom clipper.
+ **
+ **---------------------------------------------------------------------------
+ ** Copyright 2003 Tim Stump
+ ** All rights reserved.
+ **
+ ** Redistribution and use in source and binary forms, with or without
+ ** modification, are permitted provided that the following conditions
+ ** are met:
+ **
+ ** 1. Redistributions of source code must retain the above copyright
+ **    notice, this list of conditions and the following disclaimer.
+ ** 2. Redistributions in binary form must reproduce the above copyright
+ **    notice, this list of conditions and the following disclaimer in the
+ **    documentation and/or other materials provided with the distribution.
+ ** 3. The name of the author may not be used to endorse or promote products
+ **    derived from this software without specific prior written permission.
+ **
+ ** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ ** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ ** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ ** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ ** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ ** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ **---------------------------------------------------------------------------
+ **
+ */
+
+#include <math.h>
+#include "../v_video.h"
+#include "hw_clip.h"
+#include "hw_glob.h"
+#include "../r_state.h"
+#include "../tables.h"
+#include "r_opengl/r_opengl.h"
+
+#ifdef HAVE_SPHEREFRUSTRUM
+static GLdouble viewMatrix[16];
+static GLdouble projMatrix[16];
+float frustum[6][4];
+#endif
+
+typedef struct clipnode_s
+	{
+		struct clipnode_s *prev, *next;
+		angle_t start, end;
+	} clipnode_t;
+
+clipnode_t *freelist;
+clipnode_t *clipnodes;
+clipnode_t *cliphead;
+
+static clipnode_t * HWR_clipnode_GetNew(void);
+static clipnode_t * HWR_clipnode_NewRange(angle_t start, angle_t end);
+static boolean HWR_clipper_IsRangeVisible(angle_t startAngle, angle_t endAngle);
+static void HWR_clipper_AddClipRange(angle_t start, angle_t end);
+static void HWR_clipper_RemoveRange(clipnode_t * range);
+static void HWR_clipnode_Free(clipnode_t *node);
+
+static clipnode_t * HWR_clipnode_GetNew(void)
+{
+	if (freelist)
+	{
+		clipnode_t * p = freelist;
+		freelist = p->next;
+		return p;
+	}
+	else
+	{
+		return (clipnode_t*)malloc(sizeof(clipnode_t));
+	}
+}
+
+static clipnode_t * HWR_clipnode_NewRange(angle_t start, angle_t end)
+{
+	clipnode_t * c = HWR_clipnode_GetNew();
+	c->start = start;
+	c->end = end;
+	c->next = c->prev=NULL;
+	return c;
+}
+
+boolean HWR_clipper_SafeCheckRange(angle_t startAngle, angle_t endAngle)
+{
+	if(startAngle > endAngle)
+	{
+		return (HWR_clipper_IsRangeVisible(startAngle, ANGLE_MAX) || HWR_clipper_IsRangeVisible(0, endAngle));
+	}
+
+	return HWR_clipper_IsRangeVisible(startAngle, endAngle);
+}
+
+static boolean HWR_clipper_IsRangeVisible(angle_t startAngle, angle_t endAngle)
+{
+	clipnode_t *ci;
+	ci = cliphead;
+
+	if (endAngle == 0 && ci && ci->start == 0)
+		return false;
+
+	while (ci != NULL && ci->start < endAngle)
+	{
+		if (startAngle >= ci->start && endAngle <= ci->end)
+		{
+			return false;
+		}
+		ci = ci->next;
+	}
+
+	return true;
+}
+
+static void HWR_clipnode_Free(clipnode_t *node)
+{
+	node->next = freelist;
+	freelist = node;
+}
+
+static void HWR_clipper_RemoveRange(clipnode_t *range)
+{
+	if (range == cliphead)
+	{
+		cliphead = cliphead->next;
+	}
+	else
+	{
+		if (range->prev)
+		{
+			range->prev->next = range->next;
+		}
+		if (range->next)
+		{
+			range->next->prev = range->prev;
+		}
+	}
+
+	HWR_clipnode_Free(range);
+}
+
+void HWR_clipper_SafeAddClipRange(angle_t startangle, angle_t endangle)
+{
+	if(startangle > endangle)
+	{
+		// The range has to added in two parts.
+		HWR_clipper_AddClipRange(startangle, ANGLE_MAX);
+		HWR_clipper_AddClipRange(0, endangle);
+	}
+	else
+	{
+		// Add the range as usual.
+		HWR_clipper_AddClipRange(startangle, endangle);
+	}
+}
+
+static void HWR_clipper_AddClipRange(angle_t start, angle_t end)
+{
+	clipnode_t *node, *temp, *prevNode, *node2, *delnode;
+
+	if (cliphead)
+	{
+		//check to see if range contains any old ranges
+		node = cliphead;
+		while (node != NULL && node->start < end)
+		{
+			if (node->start >= start && node->end <= end)
+			{
+				temp = node;
+				node = node->next;
+				HWR_clipper_RemoveRange(temp);
+			}
+			else
+			{
+				if (node->start <= start && node->end >= end)
+				{
+					return;
+				}
+				else
+				{
+					node = node->next;
+				}
+			}
+		}
+
+		//check to see if range overlaps a range (or possibly 2)
+		node = cliphead;
+		while (node != NULL && node->start <= end)
+		{
+			if (node->end >= start)
+			{
+				// we found the first overlapping node
+				if (node->start > start)
+				{
+					// the new range overlaps with this node's start point
+					node->start = start;
+				}
+				if (node->end < end)
+				{
+					node->end = end;
+				}
+
+				node2 = node->next;
+				while (node2 && node2->start <= node->end)
+				{
+					if (node2->end > node->end)
+					{
+						node->end = node2->end;
+					}
+
+					delnode = node2;
+					node2 = node2->next;
+					HWR_clipper_RemoveRange(delnode);
+				}
+				return;
+			}
+			node = node->next;
+		}
+
+		//just add range
+		node = cliphead;
+		prevNode = NULL;
+		temp = HWR_clipnode_NewRange(start, end);
+		while (node != NULL && node->start < end)
+		{
+			prevNode = node;
+			node = node->next;
+		}
+		temp->next = node;
+		if (node == NULL)
+		{
+			temp->prev = prevNode;
+			if (prevNode)
+			{
+				prevNode->next = temp;
+			}
+			if (!cliphead)
+			{
+				cliphead = temp;
+			}
+		}
+		else
+		{
+			if (node == cliphead)
+			{
+				cliphead->prev = temp;
+				cliphead = temp;
+			}
+			else
+			{
+				temp->prev = prevNode;
+				prevNode->next = temp;
+				node->prev = temp;
+			}
+		}
+	}
+	else
+	{
+		temp = HWR_clipnode_NewRange(start, end);
+		cliphead = temp;
+		return;
+	}
+}
+
+void HWR_clipper_Clear(void)
+{
+	clipnode_t *node = cliphead;
+	clipnode_t *temp;
+
+	while (node != NULL)
+	{
+		temp = node;
+		node = node->next;
+		HWR_clipnode_Free(temp);
+	}
+
+	cliphead = NULL;
+}
+
+#define RMUL (1.6f/1.333333f)
+
+angle_t HWR_FrustumAngle(void)
+{
+	double floatangle;
+	angle_t a1;
+
+	float tilt = (float)fabs(((double)(int)aimingangle) / ANG1);
+
+	// NEWCLIP TODO: SRB2CBTODO: make a global render_fov for this function
+
+	float render_fov = FIXED_TO_FLOAT(cv_grfov.value);
+	float render_fovratio = (float)BASEVIDWIDTH / (float)BASEVIDHEIGHT; // SRB2CBTODO: NEWCLIPTODO: Is this right?
+	float render_multiplier = 64.0f / render_fovratio / RMUL;
+
+	if (tilt > 90.0f)
+	{
+		tilt = 90.0f;
+	}
+
+	// If the pitch is larger than this you can look all around at a FOV of 90
+	if (abs(aimingangle) > 46 * ANG1)
+		return 0xffffffff;
+
+	// ok, this is a gross hack that barely works...
+	// but at least it doesn't overestimate too much...
+	floatangle = 2.0f + (45.0f + (tilt / 1.9f)) * (float)render_fov * 48.0f / render_multiplier / 90.0f;
+	a1 = ANG1 * (int)floatangle;
+	if (a1 >= ANGLE_180)
+		return 0xffffffff;
+	return a1;
+}
+
+// SRB2CB I don't think used any of this stuff, let's disable for now since SRB2 probably doesn't want it either
+// compiler complains about (p)glGetDoublev anyway, in case anyone wants this
+// only r_opengl.c can use the base gl funcs as it turns out, that's a problem for whoever wants sphere frustum checks
+// btw to renable define HAVE_SPHEREFRUSTRUM in hw_clip.h
+#ifdef HAVE_SPHEREFRUSTRUM
+//
+// HWR_FrustrumSetup
+//
+
+#define CALCMATRIX(a, b, c, d, e, f, g, h)\
+(float)(viewMatrix[a] * projMatrix[b] + \
+viewMatrix[c] * projMatrix[d] + \
+viewMatrix[e] * projMatrix[f] + \
+viewMatrix[g] * projMatrix[h])
+
+#define NORMALIZE_PLANE(i)\
+t = (float)sqrt(\
+frustum[i][0] * frustum[i][0] + \
+frustum[i][1] * frustum[i][1] + \
+frustum[i][2] * frustum[i][2]); \
+frustum[i][0] /= t; \
+frustum[i][1] /= t; \
+frustum[i][2] /= t; \
+frustum[i][3] /= t
+
+void HWR_FrustrumSetup(void)
+{
+	float t;
+	float clip[16];
+
+	pglGetDoublev(GL_PROJECTION_MATRIX, projMatrix);
+	pglGetDoublev(GL_MODELVIEW_MATRIX, viewMatrix);
+
+	clip[0]  = CALCMATRIX(0, 0, 1, 4, 2, 8, 3, 12);
+	clip[1]  = CALCMATRIX(0, 1, 1, 5, 2, 9, 3, 13);
+	clip[2]  = CALCMATRIX(0, 2, 1, 6, 2, 10, 3, 14);
+	clip[3]  = CALCMATRIX(0, 3, 1, 7, 2, 11, 3, 15);
+
+	clip[4]  = CALCMATRIX(4, 0, 5, 4, 6, 8, 7, 12);
+	clip[5]  = CALCMATRIX(4, 1, 5, 5, 6, 9, 7, 13);
+	clip[6]  = CALCMATRIX(4, 2, 5, 6, 6, 10, 7, 14);
+	clip[7]  = CALCMATRIX(4, 3, 5, 7, 6, 11, 7, 15);
+
+	clip[8]  = CALCMATRIX(8, 0, 9, 4, 10, 8, 11, 12);
+	clip[9]  = CALCMATRIX(8, 1, 9, 5, 10, 9, 11, 13);
+	clip[10] = CALCMATRIX(8, 2, 9, 6, 10, 10, 11, 14);
+	clip[11] = CALCMATRIX(8, 3, 9, 7, 10, 11, 11, 15);
+
+	clip[12] = CALCMATRIX(12, 0, 13, 4, 14, 8, 15, 12);
+	clip[13] = CALCMATRIX(12, 1, 13, 5, 14, 9, 15, 13);
+	clip[14] = CALCMATRIX(12, 2, 13, 6, 14, 10, 15, 14);
+	clip[15] = CALCMATRIX(12, 3, 13, 7, 14, 11, 15, 15);
+
+	// Right plane
+	frustum[0][0] = clip[ 3] - clip[ 0];
+	frustum[0][1] = clip[ 7] - clip[ 4];
+	frustum[0][2] = clip[11] - clip[ 8];
+	frustum[0][3] = clip[15] - clip[12];
+	NORMALIZE_PLANE(0);
+
+	// Left plane
+	frustum[1][0] = clip[ 3] + clip[ 0];
+	frustum[1][1] = clip[ 7] + clip[ 4];
+	frustum[1][2] = clip[11] + clip[ 8];
+	frustum[1][3] = clip[15] + clip[12];
+	NORMALIZE_PLANE(1);
+
+	// Bottom plane
+	frustum[2][0] = clip[ 3] + clip[ 1];
+	frustum[2][1] = clip[ 7] + clip[ 5];
+	frustum[2][2] = clip[11] + clip[ 9];
+	frustum[2][3] = clip[15] + clip[13];
+	NORMALIZE_PLANE(2);
+
+	// Top plane
+	frustum[3][0] = clip[ 3] - clip[ 1];
+	frustum[3][1] = clip[ 7] - clip[ 5];
+	frustum[3][2] = clip[11] - clip[ 9];
+	frustum[3][3] = clip[15] - clip[13];
+	NORMALIZE_PLANE(3);
+
+	// Far plane
+	frustum[4][0] = clip[ 3] - clip[ 2];
+	frustum[4][1] = clip[ 7] - clip[ 6];
+	frustum[4][2] = clip[11] - clip[10];
+	frustum[4][3] = clip[15] - clip[14];
+	NORMALIZE_PLANE(4);
+
+	// Near plane
+	frustum[5][0] = clip[ 3] + clip[ 2];
+	frustum[5][1] = clip[ 7] + clip[ 6];
+	frustum[5][2] = clip[11] + clip[10];
+	frustum[5][3] = clip[15] + clip[14];
+	NORMALIZE_PLANE(5);
+}
+
+boolean HWR_SphereInFrustum(float x, float y, float z, float radius)
+{
+	int p;
+
+	for (p = 0; p < 4; p++)
+	{
+		if (frustum[p][0] * x +
+			frustum[p][1] * y +
+			frustum[p][2] * z +
+			frustum[p][3] <= -radius)
+		{
+			return false;
+		}
+	}
+	return true;
+}
+#endif
diff --git a/src/hardware/hw_clip.h b/src/hardware/hw_clip.h
new file mode 100644
index 000000000..c55041b7e
--- /dev/null
+++ b/src/hardware/hw_clip.h
@@ -0,0 +1,24 @@
+/*
+ *  hw_clip.h
+ *  SRB2CB
+ *
+ *  PrBoom's OpenGL clipping
+ *
+ *
+ */
+
+// OpenGL BSP clipping
+#include "../doomdef.h"
+#include "../tables.h"
+#include "../doomtype.h"
+
+//#define HAVE_SPHEREFRUSTRUM // enable if you want HWR_SphereInFrustum and related code
+
+boolean HWR_clipper_SafeCheckRange(angle_t startAngle, angle_t endAngle);
+void HWR_clipper_SafeAddClipRange(angle_t startangle, angle_t endangle);
+void HWR_clipper_Clear(void);
+angle_t HWR_FrustumAngle(void);
+#ifdef HAVE_SPHEREFRUSTRUM
+void HWR_FrustrumSetup(void);
+boolean HWR_SphereInFrustum(float x, float y, float z, float radius);
+#endif