diff --git a/display.c b/display.c
index 13dec1b..307c4a3 100644
--- a/display.c
+++ b/display.c
@@ -1,5 +1,6 @@
 #include "common.h"
 #include "display.h"
+#include "frustum.h"
 
 #include <inline_c.h>
 
@@ -177,6 +178,9 @@ void display_start()
 
 	// Compose view and projection matrices to obtain a combined view-projection matrix
 	CompMatrixLV(&proj_matrix, &view_matrix, &vp_matrix);
+
+	int screenheight = (GetVideoMode() == MODE_NTSC) ? SCREENHEIGHT_NTSC : SCREENHEIGHT_PAL;
+	frustum_update(&view_matrix, (SCREENWIDTH << 12) / aspect_scale.vx, (screenheight << 12) / aspect_scale.vy);
 }
 
 void display_finish()
diff --git a/frustum.c b/frustum.c
new file mode 100644
index 0000000..74969d2
--- /dev/null
+++ b/frustum.c
@@ -0,0 +1,56 @@
+#include "common.h"
+#include "frustum.h"
+#include "display.h"
+
+#include <inline_c.h>
+
+static SVECTOR left, right, top, bottom;
+
+static INLINE void frustum_buildPlane(MATRIX *view_matrix, VECTOR *normal, SVECTOR *outPlane)
+{
+    ApplyMatrixLV(view_matrix, normal, normal);
+    VectorNormalS(normal, outPlane);
+    outPlane->pad = m_dot12(cam_pos, *outPlane);
+}
+
+void frustum_update(MATRIX *view_matrix, int width, int height)
+{
+    VECTOR l, r, t, b;
+
+    int near;
+    gte_ReadGeomScreen(&near);
+    
+    //FntPrint(-1, "N = %d, W = %d, H = %d\n", near, width, height);
+
+    // 2 * near, shifted left for division
+    near <<= 13;
+
+    l.vx = near / width;
+    l.vy = ONE;
+    l.vz = 0;
+    
+    b.vx = 0;
+    b.vy = ONE;
+    b.vz = near / height;
+    
+    r.vx = -l.vx;
+    r.vy = ONE;
+    r.vz = 0;
+    
+    t.vx = 0;
+    t.vy = ONE;
+    t.vz = -b.vz;
+
+    frustum_buildPlane(view_matrix, &l, &left);
+    frustum_buildPlane(view_matrix, &r, &right);
+    frustum_buildPlane(view_matrix, &t, &top);
+    frustum_buildPlane(view_matrix, &b, &bottom);
+
+    // FntPrint(-1, "l = %d %d, r = %d %d, t = %d %d, b = %d %d\n", 
+    //     left.vx, left.pad, right.vx, right.pad, top.vz, top.pad, bottom.vz, bottom.pad);
+}
+
+u_char frustum_checkSphere(SVECTOR *sphere)
+{
+    return 1;
+}
diff --git a/frustum.h b/frustum.h
new file mode 100644
index 0000000..99f507c
--- /dev/null
+++ b/frustum.h
@@ -0,0 +1,7 @@
+#ifndef __FRUSTUM_H__
+#define __FRUSTUM_H__
+
+void frustum_update(MATRIX *view_matrix, int width, int height);
+u_char frustum_checkSphere(SVECTOR *sphere);
+
+#endif  // __FRUSTUM_H__
diff --git a/qmath.h b/qmath.h
index 1839310..bd9ecd7 100644
--- a/qmath.h
+++ b/qmath.h
@@ -3,10 +3,7 @@
 
 MATRIX *RotMatrixQ(SVECTOR *r, MATRIX *m);
 
-INLINE int m_dot12s(const SVECTOR a, const SVECTOR b)
-{
-    return (((int)a.vx * b.vx) >> 12) + (((int)a.vy * b.vy) >> 12) + (((int)a.vz * b.vz) >> 12);
-}
+#define m_dot12(a, b)   ((((int)(a).vx * (b).vx) >> 12) + (((int)(a).vy * (b).vy) >> 12) + (((int)(a).vz * (b).vz) >> 12))
 
 // TODO: worth a benchmark: is it faster to copy these vectors and use them from the stack, or to do six pointer dereferences?
 INLINE int m_pointPlaneDist2(const VECTOR point2, const SVECTOR normal12, int dist2)
diff --git a/world.c b/world.c
index d34182b..c2d4518 100644
--- a/world.c
+++ b/world.c
@@ -66,7 +66,7 @@ static INLINE short world_planeDot(const SVECTOR *dir, const ps1bsp_plane_t *pla
     if (plane->type < 3)
         return ((short*)dir)[plane->type];
 
-    return (short)m_dot12s(*dir, plane->normal);
+    return (short)m_dot12(*dir, plane->normal);
 }
 
 static INLINE char world_cull_backface(const world_t *world, const ps1bsp_face_t *face, short *dot)
@@ -78,8 +78,10 @@ static INLINE char world_cull_backface(const world_t *world, const ps1bsp_face_t
     cam_vec.vy = face->center.vy - cam_pos.vy;
     cam_vec.vz = face->center.vz - cam_pos.vz;
 
-    // Check if the face is behind the camera
-    short camDot = m_dot12s(cam_vec, cam_dir);
+    // Check if the face is behind the camera 
+    // TODO: this may cull faces close to the camera, use VectorNormalS to normalize and check for angles < -60 degrees
+    // TODO: or, just check against all corners of the face...
+    short camDot = m_dot12(cam_vec, cam_dir);
     if (camDot < 0)
         return 1;
     
@@ -199,6 +201,7 @@ static void world_drawnode(const world_t *world, short nodeIdx, u_char *pvs)
             ps1bsp_face_t *face = &world->faces[*leafFace];
 
             // Check if we've already drawn this face on the current frame
+            // NOTE: this can cause sorting issues when rendering front-to-back with leaf-based depth
             if (face->drawFrame == frameNum)
                 continue;
 
@@ -214,6 +217,7 @@ static void world_drawnode(const world_t *world, short nodeIdx, u_char *pvs)
     short dist = world_pointPlaneDist(&cam_pos, plane);
     
     // Draw child nodes in front-to-back order; adding faces to the OT will reverse the drawing order
+    // PLAN: traverse back-to-front to determine leaf order & depth, then draw faces front-to-back with primbuf checks
     char order = dist < 0;
     world_drawnode(world, node->children[order], pvs);
     world_drawnode(world, node->children[order ^ 1], pvs);
@@ -282,8 +286,6 @@ static u_short world_leafAtPoint(const world_t *world, const VECTOR *point)
 
 void world_draw(const world_t *world)
 {
-    int p;
-
     // The world doesn't move, so we just set the camera view-projection matrix
     gte_SetRotMatrix(&vp_matrix);
 	gte_SetTransMatrix(&vp_matrix);