diff --git a/common/custom_data/TFrag3Data.cpp b/common/custom_data/TFrag3Data.cpp
index 939eb39139..ef723d2059 100644
--- a/common/custom_data/TFrag3Data.cpp
+++ b/common/custom_data/TFrag3Data.cpp
@@ -579,6 +579,11 @@ void MercModelGroup::serialize(Serializer& ser) {
   ser.from_pod_vector(&vertices);
 }
 
+void DebugVisData::serialize(Serializer& ser) {
+  ser.from_pod_vector(&bsp_cell_vertices);
+  ser.from_pod_vector(&bsp_cell_indices);
+}
+
 void Level::serialize(Serializer& ser) {
   ser.from_ptr(&version);
   if (ser.is_loading() && version != TFRAG3_VERSION) {
@@ -642,6 +647,7 @@ void Level::serialize(Serializer& ser) {
 
   collision.serialize(ser);
   merc_data.serialize(ser);
+  debug_data.serialize(ser);
 
   ser.from_ptr(&version2);
   if (ser.is_loading() && version2 != TFRAG3_VERSION) {
@@ -762,6 +768,11 @@ void Hfragment::memory_usage(tfrag3::MemoryUsageTracker* tracker) const {
   tracker->add(MemoryUsageCategory::HFRAG_CORNERS, corners.size() * sizeof(HfragmentCorner));
 }
 
+void DebugVisData::memory_usage(MemoryUsageTracker* tracker) const {
+  tracker->add(MemoryUsageCategory::DEBUG_VIS, bsp_cell_indices.size() * sizeof(u32));
+  tracker->add(MemoryUsageCategory::DEBUG_VIS, bsp_cell_vertices.size() * sizeof(BspVisVertex));
+}
+
 void Level::memory_usage(MemoryUsageTracker* tracker) const {
   for (const auto& texture : textures) {
     texture.memory_usage(tracker);
@@ -785,6 +796,7 @@ void Level::memory_usage(MemoryUsageTracker* tracker) const {
   hfrag.memory_usage(tracker);
   collision.memory_usage(tracker);
   merc_data.memory_usage(tracker);
+  debug_data.memory_usage(tracker);
 }
 
 void print_memory_usage(const tfrag3::Level& lev, int uncompressed_data_size) {
@@ -829,9 +841,8 @@ void print_memory_usage(const tfrag3::Level& lev, int uncompressed_data_size) {
       {"hfrag-verts", mem_use.data[tfrag3::MemoryUsageCategory::HFRAG_VERTS]},
       {"hfrag-index", mem_use.data[tfrag3::MemoryUsageCategory::HFRAG_INDEX]},
       {"hfrag-time-of-day", mem_use.data[tfrag3::MemoryUsageCategory::HFRAG_TIME_OF_DAY]},
-      {"hfrag-corners", mem_use.data[tfrag3::MemoryUsageCategory::HFRAG_CORNERS]}
-
-  };
+      {"hfrag-corners", mem_use.data[tfrag3::MemoryUsageCategory::HFRAG_CORNERS]},
+      {"debug-vis", mem_use.data[tfrag3::MemoryUsageCategory::DEBUG_VIS]}};
   for (auto& known : known_categories) {
     total_accounted += known.second;
   }
diff --git a/common/custom_data/Tfrag3Data.h b/common/custom_data/Tfrag3Data.h
index 2dac7cf479..e2679d5747 100644
--- a/common/custom_data/Tfrag3Data.h
+++ b/common/custom_data/Tfrag3Data.h
@@ -18,7 +18,7 @@ namespace tfrag3 {
 // - if changing any large things (vertices, vis, bvh, colors, textures) update get_memory_usage
 // - if adding a new category to the memory usage, update extract_level to print it.
 
-constexpr int TFRAG3_VERSION = 43;
+constexpr int TFRAG3_VERSION = 44;
 
 enum MemoryUsageCategory {
   TEXTURE,
@@ -67,6 +67,7 @@ enum MemoryUsageCategory {
   HFRAG_CORNERS,
 
   COLLISION,
+  DEBUG_VIS,
 
   NUM_CATEGORIES
 };
@@ -614,6 +615,19 @@ struct MercModelGroup {
   void memory_usage(MemoryUsageTracker* tracker) const;
 };
 
+struct BspVisVertex {
+  float x, y, z;
+  u16 bsp_cell;
+};
+static_assert(sizeof(BspVisVertex) == 16);
+
+struct DebugVisData {
+  std::vector<BspVisVertex> bsp_cell_vertices;
+  std::vector<uint32_t> bsp_cell_indices;
+  void serialize(Serializer& ser);
+  void memory_usage(MemoryUsageTracker* tracker) const;
+};
+
 //
 
 constexpr int TFRAG_GEOS = 3;
@@ -630,6 +644,7 @@ struct Level {
   Hfragment hfrag;
   CollisionMesh collision;
   MercModelGroup merc_data;
+  DebugVisData debug_data;
   u16 version2 = TFRAG3_VERSION;
   void serialize(Serializer& ser);
   void memory_usage(MemoryUsageTracker* tracker) const;
diff --git a/decompiler/CMakeLists.txt b/decompiler/CMakeLists.txt
index 7e6f1403d6..835312c194 100644
--- a/decompiler/CMakeLists.txt
+++ b/decompiler/CMakeLists.txt
@@ -58,6 +58,7 @@ add_library(
         level_extractor/extract_actors.cpp
         level_extractor/extract_collide_frags.cpp
         level_extractor/extract_common.cpp
+        level_extractor/extract_debug_vis.cpp
         level_extractor/extract_hfrag.cpp
         level_extractor/extract_joint_group.cpp
         level_extractor/extract_level.cpp
diff --git a/decompiler/level_extractor/BspHeader.cpp b/decompiler/level_extractor/BspHeader.cpp
index f69c4eef99..6a4d052fa3 100644
--- a/decompiler/level_extractor/BspHeader.cpp
+++ b/decompiler/level_extractor/BspHeader.cpp
@@ -1995,6 +1995,92 @@ void AdgifShaderArray::read_from_file(TypedRef ref, const decompiler::Decompiler
                     sizeof(AdGifData) * length);
 }
 
+Jak1BspNodeRef bsp_node_ref_from_file(Ref node_array,
+                                      TypedRef parent,
+                                      bool is_front,
+                                      const decompiler::DecompilerTypeSystem& dts) {
+  const char* name = is_front ? "front" : "back";
+  auto type = get_word_kind_for_field(parent, name, dts);
+  Jak1BspNodeRef ret;
+  if (type == decompiler::LinkedWord::PTR) {
+    ret.is_leaf = false;
+    Ref child = deref_label(get_field_ref(parent, name, dts));
+    int byte_offset = child.byte_offset - node_array.byte_offset;
+    ASSERT((byte_offset & 31) == 0);
+    ret.index = byte_offset / 32;
+  } else if (type == decompiler::LinkedWord::PLAIN_DATA) {
+    ret.is_leaf = true;
+    uint32_t leaf_value = read_plain_data_field<uint32_t>(parent, name, dts);
+    ASSERT((leaf_value >> 16) == 0x8000);
+    ret.index = leaf_value & 0xffff;
+  } else {
+    ASSERT_NOT_REACHED();
+  }
+  return ret;
+}
+
+Jak1BspNode bsp_node_from_file(Ref node_array,
+                               Ref ref,
+                               const decompiler::DecompilerTypeSystem& dts) {
+  Jak1BspNode result;
+  TypedRef r(ref, dts.ts.lookup_type("bsp-node"));
+  result.front = bsp_node_ref_from_file(node_array, r, true, dts);
+  result.back = bsp_node_ref_from_file(node_array, r, false, dts);
+  result.front_flags = read_plain_data_field<uint32_t>(r, "front-flags", dts);
+  result.back_flags = read_plain_data_field<uint32_t>(r, "back-flags", dts);
+  result.plane.read_from_file(get_field_ref(r, "plane", dts));
+  result.discovered = true;
+  return result;
+}
+
+void print_node(const Jak1BspNode& node) {
+  fmt::print("[{:.3f} {:.3f} {:.3f} {:.3f}] ({} {} {}) ({} {} {})\n",
+    node.plane.data[0], node.plane.data[1], node.plane.data[2], node.plane.data[3],
+    node.front.is_leaf, node.front.index, node.front_flags,
+    node.back.is_leaf,  node.back.index, node.back_flags
+    );
+}
+
+std::vector<Jak1BspNode> bsp_nodes_from_file(Ref node_array,
+                                             const decompiler::DecompilerTypeSystem& dts) {
+  std::vector<Jak1BspNode> nodes;
+  std::vector<int> to_explore = {0};
+
+  while (!to_explore.empty()) {
+    int node_idx = to_explore.back();
+    to_explore.pop_back();
+
+    // expand node array
+    if (nodes.size() <= node_idx) {
+      nodes.resize(node_idx + 1);
+    }
+
+    if (nodes.at(node_idx).discovered) {
+      continue;
+    }
+
+    Ref node_ref = node_array;
+    node_ref.byte_offset += 32 * node_idx;
+    nodes.at(node_idx) = bsp_node_from_file(node_array, node_ref, dts);
+    auto& n = nodes.at(node_idx);
+    if (!n.front.is_leaf) {
+      to_explore.push_back(n.front.index);
+    }
+    if (!n.back.is_leaf) {
+      to_explore.push_back(n.back.index);
+    }
+    // print_node(nodes.at(node_idx));
+
+  }
+
+  int known = 0;
+  for (auto& n : nodes) {
+    if (n.discovered) known++;
+  }
+  ASSERT((int)nodes.size() == known);
+  return nodes;
+}
+
 void BspHeader::read_from_file(const decompiler::LinkedObjectFile& file,
                                const decompiler::DecompilerTypeSystem& dts,
                                GameVersion version,
@@ -2012,6 +2098,7 @@ void BspHeader::read_from_file(const decompiler::LinkedObjectFile& file,
   if (version == GameVersion::Jak1) {
     adgifs.read_from_file(get_and_check_ref_to_basic(ref, "adgifs", "adgif-shader-array", dts),
                           dts);
+    jak1_bsp_nodes = bsp_nodes_from_file(deref_label(get_field_ref(ref, "nodes", dts)), dts);
   }
 
   texture_page_count = read_plain_data_field<s32>(ref, "texture-page-count", dts);
diff --git a/decompiler/level_extractor/BspHeader.h b/decompiler/level_extractor/BspHeader.h
index e0b47969ff..367e921290 100644
--- a/decompiler/level_extractor/BspHeader.h
+++ b/decompiler/level_extractor/BspHeader.h
@@ -862,6 +862,22 @@ struct FileInfo {
   std::string print(int indent = 0) const;
 };
 
+struct Jak1BspNodeRef {
+  bool is_leaf = false;
+  int index = 0;
+};
+
+struct Jak1BspNode {
+  Jak1BspNodeRef front;
+  Jak1BspNodeRef back;
+
+  uint32_t front_flags = 0;
+  uint32_t back_flags = 0;
+  Vector plane;
+
+  bool discovered = false;
+};
+
 struct BspHeader {
   //  (info file-info :offset 4)
   FileInfo file_info;
@@ -904,6 +920,7 @@ struct BspHeader {
   DrawableInlineArrayActor actors;
   //  (cameras (array entity-camera) :offset-assert 116)
   //  (nodes (inline-array bsp-node) :offset-assert 120)
+  std::vector<Jak1BspNode> jak1_bsp_nodes;
   //
   //  (level level :offset-assert 124)
   //  (current-leaf-idx uint16 :offset-assert 128)
diff --git a/decompiler/level_extractor/extract_debug_vis.cpp b/decompiler/level_extractor/extract_debug_vis.cpp
new file mode 100644
index 0000000000..c8227ccb94
--- /dev/null
+++ b/decompiler/level_extractor/extract_debug_vis.cpp
@@ -0,0 +1,703 @@
+#include "extract_debug_vis.h"
+
+#include "common/log/log.h"
+#include "common/math/Vector.h"
+
+namespace {
+
+using Point = math::Vector3d;
+using Plane = math::Vector4d;  // Plane(a, b, c, d) -> ax + by + cz = d
+
+Plane flip_plane_normal(const Plane& in) {
+  return in * -1;
+}
+
+math::Vector3d plane_normal(const Plane& in) {
+  return in.xyz();
+}
+
+math::Vector4d convert_vector(const level_tools::Vector& in) {
+  return math::Vector4d(in.data[0], in.data[1], in.data[2], in.data[3]);
+}
+
+double point_plane_check(const Point& pt, const Plane& plane) {
+  return pt.x() * plane.x() + pt.y() * plane.y() + pt.z() * plane.z() - plane.w();
+}
+
+/*!
+ * Find the largest leaf index.
+ */
+int max_leaf_idx(const std::vector<level_tools::Jak1BspNode>& nodes) {
+  int ret = -1;
+  for (auto& node : nodes) {
+    if (node.back.is_leaf)
+      ret = std::max(ret, node.back.index);
+    if (node.front.is_leaf)
+      ret = std::max(ret, node.front.index);
+  }
+  return ret;
+}
+
+/*!
+ * Description of the tree structure of BSP nodes.
+ */
+struct ParentData {
+  std::vector<int> node_parents;  // parent_node = node_parents[child_node]
+  std::vector<int> leaf_parents;  // parent_node = leaf_parents[leaf]
+
+  int num_leaves() const { return leaf_parents.size(); }
+};
+
+/*!
+ * Find the tree structure of BSP nodes from the array, that the BSP nodes are a tree, and there
+ * are no unparented/unused slots in either the leaf or node arrays. Things would still work if
+ * there were unused slots, but it just wastes memory and makes no sense.
+ */
+ParentData find_parents(const std::vector<level_tools::Jak1BspNode>& nodes) {
+  ParentData result;
+  result.node_parents.resize(nodes.size(), -1);
+  result.leaf_parents.resize(max_leaf_idx(nodes) + 1, -1);
+
+  // start at the root:
+  std::vector<int> to_explore = {0};
+  while (!to_explore.empty()) {
+    int node_idx = to_explore.back();
+    to_explore.pop_back();
+
+    auto& n = nodes.at(node_idx);
+
+    // add parents, and assert it's the first time we've seen the child (since it's a tree)
+    // you could imagine mapping two volumes to the same leaf, but it looks like they don't
+    if (n.front.is_leaf) {
+      ASSERT(result.leaf_parents.at(n.front.index) == -1);
+      result.leaf_parents.at(n.front.index) = node_idx;
+    } else {
+      to_explore.push_back(n.front.index);
+      ASSERT(result.node_parents.at(n.front.index) == -1);
+      result.node_parents.at(n.front.index) = node_idx;
+    }
+
+    if (n.back.is_leaf) {
+      ASSERT(result.leaf_parents.at(n.back.index) == -1);
+      result.leaf_parents.at(n.back.index) = node_idx;
+    } else {
+      to_explore.push_back(n.back.index);
+      ASSERT(result.node_parents.at(n.back.index) == -1);
+      result.node_parents.at(n.back.index) = node_idx;
+    }
+  }
+
+  // check for unused slots in leaf/node arrays.
+  int unparented_leaves = 0;
+  int unparented_nodes = 0;
+  for (auto np : result.node_parents) {
+    if (np == -1)
+      unparented_nodes++;
+  }
+  for (auto lp : result.leaf_parents) {
+    if (lp == -1)
+      unparented_leaves++;
+  }
+  ASSERT(unparented_nodes == 1);   // the root is unparented
+  ASSERT(unparented_leaves == 0);  // every leaf should be the child of a
+
+  return result;
+}
+
+/*!
+ * For a given leaf, find the bounding planes. A point (x, y, z) is inside the leaf, if for all
+ * planes (a, b, c, d):
+ *
+ * ax + by + cz - d > 0
+ *
+ */
+std::vector<Plane> planes_for_leaf(int leaf_idx,
+                                   const ParentData& tree,
+                                   const std::vector<level_tools::Jak1BspNode>& nodes) {
+  std::vector<Plane> planes;
+
+  int parent_idx = tree.leaf_parents.at(leaf_idx);
+  int child_idx = leaf_idx;
+
+  // each iteration adds the plane from parent_idx, then goes up the tree.
+  while (parent_idx != -1) {
+    // printf(" p %d\n", parent_idx);
+    const auto& node = nodes.at(parent_idx);
+    if (node.back.index == child_idx) {
+      // if this is the "back" child of the parent, flip the sign of the plane - this child is
+      // if the unflipped plane check fails.
+      planes.push_back(flip_plane_normal(convert_vector(node.plane)));
+    } else if (node.front.index == child_idx) {
+      planes.push_back(convert_vector(node.plane));
+    } else {
+      ASSERT_NOT_REACHED();
+    }
+
+    int new_parent = tree.node_parents.at(parent_idx);
+    child_idx = parent_idx;
+    parent_idx = new_parent;
+  }
+
+  return planes;
+}
+
+/*!
+ * Representation of a convex face as collection of points on a plane. The winding of the points
+ * should match the normal. (do we really care about this?)
+ */
+struct Face {
+  std::vector<Point> points;
+  Plane plane;
+  void verify() const;
+  double area() const;
+  Point avg_vertex_pos() const;
+  void flip_if_needed();
+};
+
+void Face::flip_if_needed() {
+  ASSERT(points.size() > 1);
+  const Point c = avg_vertex_pos();
+  const Point ab = points.at(1) - points.at(0);
+  const Point ac = c - points.at(0);
+  const math::Vector3d abac = ab.cross(ac);
+  const double winding_check = abac.dot(plane_normal(plane));
+
+  if (winding_check < 0) {
+    std::reverse(points.begin(), points.end());
+  }
+}
+/*!
+ * Get the average of all vertices. Because the face is convex, this returns a point in the area.
+ */
+Point Face::avg_vertex_pos() const {
+  Point ret = Point::zero();
+  for (auto& p : points) {
+    ret += p;
+  }
+  ret /= double(points.size());
+  return ret;
+}
+
+/*!
+ * Get the area of the face, also checking the winding order.
+ */
+double Face::area() const {
+  // let c be any point inside the face:
+  const Point c = avg_vertex_pos();
+
+  double total = 0;
+
+  for (int ai = 0; ai < points.size(); ai++) {
+    const int bi = (ai + 1) % points.size();
+    const Point ab = points.at(bi) - points.at(ai);
+    const Point ac = c - points.at(ai);
+    const math::Vector3d abac = ab.cross(ac);
+    const double winding_check = abac.dot(plane_normal(plane));
+    if (winding_check < 0) {
+      lg::die("winding check failed");
+    }
+    // printf("abac: %f\n", abac.length());
+    total += abac.length();
+  }
+  return total * 0.5;
+}
+
+/*!
+ * Verify that a face is valid: all points lie on the plane and the winding order is correct.
+ */
+void Face::verify() const {
+  // verify that all points lie on the plane.
+  for (const auto& pt : points) {
+    const double dist_from_plane = point_plane_check(pt, plane);
+    if (std::abs(dist_from_plane) > 200) {
+      lg::die("Point not on plane error {} {}", dist_from_plane, plane.to_string_aligned());
+    }
+  }
+
+  // checks winding:
+  const double a = area();
+  ASSERT(a > 0);
+
+  // TODO: could check for tangled stuff here?
+}
+
+/*!
+ * Representation of a volume as a collection of bounding faces.
+ */
+struct Volume {
+  std::vector<Face> faces;
+  void verify() const;
+  bool check_point_in_volume(const Point& pt) const;
+  double surface_area() const;
+  double volume() const;
+  Point some_internal_point() const;
+};
+
+/*!
+ * Is pt inside this volume?
+ */
+bool Volume::check_point_in_volume(const Point& pt) const {
+  for (auto& face : faces) {
+    if (point_plane_check(pt, face.plane) < 0) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/*!
+ * Get a point inside the volume. Average of face centers now.
+ */
+Point Volume::some_internal_point() const {
+  Point ret = Point::zero();
+  for (auto& face : faces) {
+    ret += face.avg_vertex_pos();
+  }
+  return ret /= double(faces.size());
+}
+
+/*!
+ * Verify all faces in the volume, then verify face orientation.
+ */
+void Volume::verify() const {
+  for (const auto& face : faces) {
+    face.verify();
+  }
+
+  if (!check_point_in_volume(some_internal_point())) {
+    lg::die("pt in volume verify failed");
+  }
+}
+
+/*!
+ * Compute the surface area.
+ */
+double Volume::surface_area() const {
+  double ret = 0;
+  for (const auto& face : faces) {
+    ret += face.area();
+  }
+  return ret;
+}
+
+/*!
+ * Find the volume enclosed.
+ */
+double Volume::volume() const {
+  double ret = 0;
+  Point d = some_internal_point();
+  for (const auto& face : faces) {
+    Point c = face.avg_vertex_pos();
+    for (size_t ai = 0; ai < face.points.size(); ai++) {
+      size_t bi = (ai + 1) % face.points.size();
+      Point a = face.points.at(ai);
+      Point b = face.points.at(bi);
+      ret += std::abs((a - d).dot((b - d).cross(c - d))) / 6.;
+    }
+  }
+  return ret;
+}
+
+enum class FacePlaneResult { ALL_IN, ALL_OUT, SPLIT };
+
+/*!
+ * Check a face against a plane to determine if the face is all on one side, all on the other, or in
+ * the middle.
+ */
+FacePlaneResult check_face_plane(const Face& face, const Plane& plane) {
+  bool found_in = false;
+  bool found_out = false;
+
+  for (auto& pt : face.points) {
+    if (point_plane_check(pt, plane) > 0) {
+      found_in = true;
+    } else {
+      found_out = true;
+    }
+  }
+
+  if (found_in && found_out) {
+    return FacePlaneResult::SPLIT;
+  } else if (found_in && !found_out) {
+    return FacePlaneResult::ALL_IN;
+  } else if (found_out && !found_in) {
+    return FacePlaneResult::ALL_OUT;
+  } else {
+    ASSERT_NOT_REACHED();
+  }
+}
+
+struct ClipFaceResult {
+  Face clipped_face;
+  Point a, b;  // the new points added to this face.
+};
+
+/*!
+ * Compute the intersection between a line segment and plane.
+ */
+std::optional<Point> plane_line_segment_isect(const Plane& plane,
+                                              const Point& p0,
+                                              const Point& p1,
+                                              double* u) {
+  // let p = p0 + u * (p1 - p0)
+  // if p is on the plane, then dot(p, n) = d
+  // dot(p0 + u * (p1 - p0), n) = d
+  // dot(p0, n) + u * dot(p1 - p0, n) = d
+  // u = (d - dot(p0, n)) / dot(p1 - p0, n)
+  const math::Vector3d n = plane.xyz();
+  *u = (plane.w() - p0.dot(n)) / (p1 - p0).dot(n);
+  if (*u >= 0 && *u <= 1) {
+    Point ret = p0 + (p1 - p0) * *u;
+    // fmt::print("ret dist: {}, {} {}\n", point_plane_check(ret, plane), point_plane_check(p0,
+    // plane),
+    //            point_plane_check(p1, plane));
+    return ret;
+  } else {
+    return std::nullopt;
+  }
+}
+
+/*!
+ * Clip a face, returning the new face, and the two vertices of the new face that intersect the
+ * clipping plane.
+ */
+ClipFaceResult clip_face(const Face& face, const Plane& plane) {
+  ClipFaceResult result;
+  result.clipped_face.plane = face.plane;
+
+  // determine if each point is in the new face.
+  std::vector<bool> pt_in;
+  for (auto& pt : face.points) {
+    pt_in.push_back(point_plane_check(pt, plane) > 0);
+  }
+
+  // loop around points on this face, including them in the new face only if they are inside the
+  // plane. When the permiter enters and exits the clipping plane, generate new vertices, and store
+  // these in the a/b outputs.
+  int saw_exit = 0;
+  int saw_enter = 0;
+  for (size_t i = 0; i < face.points.size(); i++) {
+    const auto p0 = face.points.at(i);
+    const auto p1 = face.points.at((i + 1) % face.points.size());
+    if (pt_in[i]) {
+      // if the point is in, just add it.
+      result.clipped_face.points.push_back(p0);
+      // exit point - need to insert a new vertex here!
+      if (!pt_in[(i + 1) % face.points.size()]) {
+        saw_exit++;
+        double u;
+        auto new_pt = plane_line_segment_isect(plane, p0, p1, &u);
+        ASSERT(new_pt.has_value());
+        // fmt::print("CLIP A: {} {} -> {} (u = {})\n", p0.to_string_aligned(),
+        // p1.to_string_aligned(),
+        //            new_pt->to_string_aligned(), u);
+        result.clipped_face.points.push_back(*new_pt);
+        result.a = *new_pt;
+      }
+    } else {
+      if (pt_in[(i + 1) % face.points.size()]) {
+        // enter
+        saw_enter++;
+        double u;
+        auto new_pt = plane_line_segment_isect(plane, p0, p1, &u);
+        ASSERT(new_pt.has_value());
+        // fmt::print("CLIP B: {} {} -> {} (u = {})\n", p0.to_string_aligned(),
+        // p1.to_string_aligned(),
+        //            new_pt->to_string_aligned(), u);
+        result.clipped_face.points.push_back(*new_pt);
+        result.b = *new_pt;
+      }
+    }
+  }
+
+  ASSERT(saw_enter == 1);
+  ASSERT(saw_exit == 1);
+  result.clipped_face.verify();
+  return result;
+}
+
+std::vector<Point> extract_face_ring(const std::vector<ClipFaceResult>& cfr) {
+  std::vector<Point> result;
+  ASSERT(cfr.size() > 1);
+  std::vector<bool> used(cfr.size(), false);
+
+  // add the first one
+  int num_used = 1;
+  used[0] = true;
+  // result.push_back(cfr[0].a);
+  result.push_back(cfr[0].b);
+
+  // for (auto& cf : cfr) {
+  //   fmt::print("{} {}\n", cf.a.to_string_aligned(), cf.b.to_string_aligned());
+  // }
+
+  // gross N^2 loop to guess at the order of the edges in the new face beacuse I didn't track face
+  // connectivity... :(
+  // printf("efr: %d %ld\n", num_used, used.size());
+  while (num_used < used.size()) {
+    const auto& tgt = result.back();
+    double best_dist = std::numeric_limits<double>::max();
+    size_t best_idx = -1;
+
+    for (size_t i = 0; i < cfr.size(); i++) {
+      // printf("checking %ld (%d)\n", i, int(used[i]));
+      if (used[i]) {
+        continue;
+      }
+      const double dist = (cfr[i].a - tgt).squared_length();
+      if (dist < best_dist) {
+        best_dist = dist;
+        best_idx = i;
+      }
+    }
+    num_used++;
+    used.at(best_idx) = true;
+    // printf("PICKED %ld\n", best_idx);
+    // ASSERT(best_dist < 4096 * 4096 * 10);  // hmm
+    result.push_back(cfr[best_idx].b);
+  }
+
+  // 0 b = [-16777216.000 16777216.000 -2211840.000]
+  // 3 a = [-16777216.000 16777216.000 -2211840.000] -> [-16777216.000 -16777216.000 -2211840.000]
+  // 1 a = [-16777216.000 -16777216.000 -2211840.000] -> [16777216.000 -16777216.000 -2211840.000]
+  // 2 a = [16777216.000 -16777216.000 -2211840.000] -> 16777216.000 16777216.000 -2211840.000]
+
+  // fmt::print("last in the result: {}\n", result.back().to_string_aligned());
+  // fmt::print("cfr[0]a           : {}\n", cfr[0].a.to_string_aligned());
+  // fmt::print("diff              : {}\n", (result.back() - cfr[0].a).to_string_aligned());
+  // fmt::print("diff              : {}\n", (result.back() - cfr[0].a).squared_length());
+
+  // ASSERT(4096 * 4096 * 10 > (result.back() - cfr[0].a).squared_length());
+  return result;
+}
+
+// TODO: paranoid clipping that checks a = b, b = a, area sums.
+
+Volume clip_volume(const Volume& vol, const Plane& plane) {
+  Volume new_volume;
+  std::vector<ClipFaceResult> split_faces;
+
+  // categorize faces
+  for (const auto& face : vol.faces) {
+    // printf("running on face\n");
+    switch (check_face_plane(face, plane)) {
+      case FacePlaneResult::ALL_IN:
+        new_volume.faces.push_back(face);
+        break;
+      case FacePlaneResult::SPLIT:
+        split_faces.push_back(clip_face(face, plane));
+        break;
+      case FacePlaneResult::ALL_OUT:
+        break;
+    }
+  }
+  size_t all_in_count = new_volume.faces.size();
+  // printf("face counts: %ld -> %ld in, %ld split\n", vol.faces.size(), all_in_count,
+  //        split_faces.size());
+  // ASSERT(!new_volume.faces.empty());
+
+  if (!split_faces.empty()) {
+    // add clipped faces
+    for (auto& cf : split_faces) {
+      new_volume.faces.push_back(cf.clipped_face);
+    }
+
+    // build the new face
+    Face new_face;
+    new_face.plane = plane;
+    new_face.points = extract_face_ring(split_faces);
+    new_face.flip_if_needed();
+    new_face.verify();
+    new_volume.faces.push_back(new_face);
+  } else {
+  }
+
+  return new_volume;
+}
+
+Volume paranoid_clip_volume(const Volume& vol, const Plane& plane) {
+  // printf("CLIP STARTING!\n");
+
+  Volume clipped = clip_volume(vol, plane);
+  clipped.verify();
+  Volume other = clip_volume(vol, flip_plane_normal(plane));
+  other.verify();
+
+  // TODO check areas
+  const double a1 = vol.surface_area();
+  const double a2 = clipped.surface_area() + other.surface_area();
+  ASSERT(a2 >= a1);  // todo: could be better.
+  const double v1 = vol.volume();
+  const double v2 = clipped.volume() + other.volume();
+  if (std::abs(v1 - v2) > 0.001 * v1) {
+    lg::die("Bad volumes: {} != {}\n", v1 / 1e6, v2 / 1e6);
+  }
+
+  // printf("CLIP Completed!\n");
+  return clipped;
+}
+
+/*!
+ * Given a sphere (x, y, z, radius), build a Volume for the axis-aligned bounding box of this
+ * sphere.
+ */
+Volume make_aabb_for_sphere(const level_tools::Vector& sphere) {
+  Volume volume;
+
+  Point origin(sphere.data[0], sphere.data[1], sphere.data[2]);
+  const double ox = origin.x();
+  const double oy = origin.y();
+  const double oz = origin.z();
+  const double r = sphere.data[3];
+
+  Face top_face;
+  top_face.plane = Plane(0, -1, 0, -oy - r);
+  top_face.points.emplace_back(ox - r, oy + r, oz - r);
+  top_face.points.emplace_back(ox + r, oy + r, oz - r);
+  top_face.points.emplace_back(ox + r, oy + r, oz + r);
+  top_face.points.emplace_back(ox - r, oy + r, oz + r);
+  volume.faces.push_back(top_face);
+
+  Face bot_face;
+  bot_face.plane = Plane(0, 1, 0, -oy - r);
+  bot_face.points.emplace_back(ox - r, oy - r, oz - r);
+  bot_face.points.emplace_back(ox - r, oy - r, oz + r);
+  bot_face.points.emplace_back(ox + r, oy - r, oz + r);
+  bot_face.points.emplace_back(ox + r, oy - r, oz - r);
+  volume.faces.push_back(bot_face);
+
+  Face s1_face;
+  s1_face.plane = Plane(-1, 0, 0, -ox - r);
+  s1_face.points.emplace_back(ox + r, oy - r, oz - r);
+  s1_face.points.emplace_back(ox + r, oy - r, oz + r);
+  s1_face.points.emplace_back(ox + r, oy + r, oz + r);
+  s1_face.points.emplace_back(ox + r, oy + r, oz - r);
+  volume.faces.push_back(s1_face);
+
+  Face s2_face;
+  s2_face.plane = Plane(1, 0, 0, -ox - r);
+  s2_face.points.emplace_back(ox - r, oy - r, oz - r);
+  s2_face.points.emplace_back(ox - r, oy + r, oz - r);
+  s2_face.points.emplace_back(ox - r, oy + r, oz + r);
+  s2_face.points.emplace_back(ox - r, oy - r, oz + r);
+  volume.faces.push_back(s2_face);
+
+  Face front_face;
+  front_face.plane = Plane(0, 0, -1, -oz - r);
+  front_face.points.emplace_back(ox - r, oy - r, oz + r);
+  front_face.points.emplace_back(ox - r, oy + r, oz + r);
+  front_face.points.emplace_back(ox + r, oy + r, oz + r);
+  front_face.points.emplace_back(ox + r, oy - r, oz + r);
+  volume.faces.push_back(front_face);
+
+  Face back_face;
+  back_face.plane = Plane(0, 0, 1, -oz - r);
+  back_face.points.emplace_back(ox - r, oy - r, oz - r);
+  back_face.points.emplace_back(ox + r, oy - r, oz - r);
+  back_face.points.emplace_back(ox + r, oy + r, oz - r);
+  back_face.points.emplace_back(ox - r, oy + r, oz - r);
+  volume.faces.push_back(back_face);
+
+  volume.verify();
+
+  const double expected_vol = 8 * r * r * r;
+  const double expected_sa = 24 * r * r;
+
+  const double vol = volume.volume();
+  const double sa = volume.surface_area();
+
+  if (std::abs(vol - expected_vol) > expected_vol * 0.001) {
+    lg::die("volume bad: {} {}\n", vol, expected_vol);
+  }
+
+  if (std::abs(sa - expected_sa) > expected_sa * 0.001) {
+    lg::die("sa bad: {} {}\n", vol, expected_vol);
+  }
+
+  // lg::print("got {} {}, {} {}\n", vol, expected_vol, sa, expected_sa);
+
+  return volume;
+}
+
+tfrag3::BspVisVertex make_vtx(const Point& pt, int leaf) {
+  tfrag3::BspVisVertex v;
+  v.bsp_cell = leaf;
+  v.x = pt.x();
+  v.y = pt.y();
+  v.z = pt.z();
+  return v;
+}
+
+void generate_volume_verts(std::vector<tfrag3::BspVisVertex>* verts,
+                           std::vector<u32>* indices,
+                           int leaf,
+                           const Volume& volume) {
+  // TODO: we could reuse vertices between faces...
+
+  for (const auto& face : volume.faces) {
+    // center
+    indices->push_back(verts->size());
+    verts->push_back(make_vtx(face.avg_vertex_pos(), leaf));
+
+    // points
+    for (const auto& pt : face.points) {
+      indices->push_back(verts->size());
+      verts->push_back(make_vtx(pt, leaf));
+    }
+
+    // next fan
+    indices->push_back(UINT32_MAX);
+  }
+}
+
+}  // namespace
+
+void extract_bsp_cells(const level_tools::BspHeader& bsp, tfrag3::Level* out) {
+  printf("bsp cells for %s %f %f %f %f\n", bsp.name.c_str(), bsp.bsphere.data[0],
+         bsp.bsphere.data[1], bsp.bsphere.data[2], bsp.bsphere.data[3]);
+
+  // ugh - bsphere seems like it's not set.
+  level_tools::Vector derp;
+  derp.data[0] = 0;
+  derp.data[1] = 0;
+  derp.data[2] = 0;
+  derp.data[3] = 4096. * 4096. * 10.;
+
+  auto parents = find_parents(bsp.jak1_bsp_nodes);
+  for (int leaf_idx = 0; leaf_idx < parents.num_leaves(); leaf_idx++) {
+    // printf("-----------------------------LEAF %d/%d\n", leaf_idx, parents.num_leaves());
+    auto planes = planes_for_leaf(leaf_idx, parents, bsp.jak1_bsp_nodes);
+    std::reverse(planes.begin(), planes.end());
+    Volume vol = make_aabb_for_sphere(derp);
+
+    for (auto& clip : planes) {
+      vol = paranoid_clip_volume(vol, clip);
+    }
+
+    bool skip = false;
+    for (auto& face : vol.faces) {
+      for (auto& pt : face.points) {
+        for (int i = 0; i < 3; i++) {
+          if (std::abs(pt[i]) > derp.data[3] * 0.8) {
+            skip = true;
+          }
+        }
+      }
+    }
+
+    if (!skip) {
+      generate_volume_verts(&out->debug_data.bsp_cell_vertices, &out->debug_data.bsp_cell_indices,
+                      leaf_idx, vol);
+    }
+
+
+
+    // ASSERT_NOT_REACHED();
+  }
+}
+
+namespace decompiler {
+void extract_debug_vis(const level_tools::BspHeader& bsp, tfrag3::Level* out) {
+  extract_bsp_cells(bsp, out);
+}
+}  // namespace decompiler
diff --git a/decompiler/level_extractor/extract_debug_vis.h b/decompiler/level_extractor/extract_debug_vis.h
new file mode 100644
index 0000000000..54203b6ad3
--- /dev/null
+++ b/decompiler/level_extractor/extract_debug_vis.h
@@ -0,0 +1,10 @@
+#pragma once
+
+#include "common/custom_data/Tfrag3Data.h"
+
+#include "decompiler/level_extractor/BspHeader.h"
+
+namespace decompiler {
+
+void extract_debug_vis(const level_tools::BspHeader& bsp, tfrag3::Level* out);
+}
\ No newline at end of file
diff --git a/decompiler/level_extractor/extract_level.cpp b/decompiler/level_extractor/extract_level.cpp
index 4cb5d8ae18..c3cd52ed0f 100644
--- a/decompiler/level_extractor/extract_level.cpp
+++ b/decompiler/level_extractor/extract_level.cpp
@@ -12,6 +12,7 @@
 #include "decompiler/level_extractor/BspHeader.h"
 #include "decompiler/level_extractor/extract_actors.h"
 #include "decompiler/level_extractor/extract_collide_frags.h"
+#include "decompiler/level_extractor/extract_debug_vis.h"
 #include "decompiler/level_extractor/extract_hfrag.h"
 #include "decompiler/level_extractor/extract_joint_group.h"
 #include "decompiler/level_extractor/extract_merc.h"
@@ -255,6 +256,10 @@ level_tools::BspHeader extract_bsp_from_level(const ObjectFileDB& db,
   if (bsp_header.hfrag) {
     extract_hfrag(bsp_header, tex_db, &level_data);
   }
+
+  if (db.version() == GameVersion::Jak1) {  // for now...
+    extract_debug_vis(bsp_header, &level_data);
+  }
   level_data.level_name = bsp_header.name;
 
   return bsp_header;
@@ -404,7 +409,7 @@ void extract_all_levels(const ObjectFileDB& db,
       [&](int idx) {
         extract_from_level(db, tex_db, dgo_names[idx], config, output_path, entities_dir);
       },
-      dgo_names.size());
+      dgo_names.size(), 1);
   threads.join();
 }
 
diff --git a/game/CMakeLists.txt b/game/CMakeLists.txt
index df32b480ad..a576cef213 100644
--- a/game/CMakeLists.txt
+++ b/game/CMakeLists.txt
@@ -39,6 +39,7 @@ set(RUNTIME_SOURCE
         graphics/opengl_renderer/background/TFragment.cpp
         graphics/opengl_renderer/background/Tie3.cpp
         graphics/opengl_renderer/BlitDisplays.cpp
+        graphics/opengl_renderer/BspRenderer.cpp
         graphics/opengl_renderer/BucketRenderer.cpp
         graphics/opengl_renderer/CollideMeshRenderer.cpp
         graphics/opengl_renderer/debug_gui.cpp
diff --git a/game/graphics/opengl_renderer/BspRenderer.cpp b/game/graphics/opengl_renderer/BspRenderer.cpp
new file mode 100644
index 0000000000..33f7cc2bf4
--- /dev/null
+++ b/game/graphics/opengl_renderer/BspRenderer.cpp
@@ -0,0 +1,139 @@
+#include "BspRenderer.h"
+
+#include "common/log/log.h"
+
+#include <third-party/imgui/imgui.h>
+
+BspRenderer::BspRenderer(GameVersion version) {
+  glGenVertexArrays(1, &m_vao);
+}
+
+void BspRenderer::render(SharedRenderState* render_state, ScopedProfilerNode& prof) {
+  // can't render
+  if (!render_state->has_pc_data) {
+    return;
+  }
+
+  // check loaded levels
+  auto levels = render_state->loader->get_in_use_levels();
+  if (levels.empty()) {
+    return;
+  }
+
+  glBindVertexArray(m_vao);
+
+  // see if we need to load meshes for any
+  for (const auto& level : levels) {
+    const auto& cached = m_level_cache.find(level->load_id);
+    if (cached == m_level_cache.end()) {
+      lg::info("BspRenderer loading for {}", level->level->level_name);
+      unload_cached_for_name(level->level->level_name);
+      load_level(level, &m_level_cache[level->load_id]);
+    }
+    render_level(render_state, prof, &m_level_cache.at(level->load_id));
+  }
+}
+
+void BspRenderer::load_level(LevelData* level, LevelCache* lc) {
+  glGenBuffers(1, &lc->vertex_buffer);
+  glGenBuffers(1, &lc->index_buffer);
+  glBindBuffer(GL_ARRAY_BUFFER, lc->vertex_buffer);
+  glBufferData(GL_ARRAY_BUFFER,
+               level->level->debug_data.bsp_cell_vertices.size() * sizeof(tfrag3::BspVisVertex),
+               level->level->debug_data.bsp_cell_vertices.data(), GL_STATIC_DRAW);
+  glBindBuffer(GL_ARRAY_BUFFER, lc->index_buffer);
+  glBufferData(GL_ARRAY_BUFFER, level->level->debug_data.bsp_cell_indices.size() * sizeof(u32),
+               level->level->debug_data.bsp_cell_indices.data(), GL_STATIC_DRAW);
+  lc->index_count = level->level->debug_data.bsp_cell_indices.size();
+}
+
+void BspRenderer::unload_cached_for_name(const std::string& name) {
+  for (auto it = m_level_cache.begin(); it != m_level_cache.end();) {
+    if (it->second.name == name) {
+      lg::info("BspRenderer first removing loaded {}", name);
+      unload_level(&it->second);
+      it = m_level_cache.erase(it);
+    } else {
+      ++it;
+    }
+  }
+}
+
+void BspRenderer::unload_level(LevelCache* lc) {
+  glDeleteBuffers(1, &lc->index_buffer);
+  glDeleteBuffers(1, &lc->vertex_buffer);
+}
+
+BspRenderer::~BspRenderer() {
+  glDeleteVertexArrays(1, &m_vao);
+}
+
+void BspRenderer::draw_debug_window() {
+  ImGui::InputInt("min-leaf", &min_leaf);
+  ImGui::InputInt("max-leaf", &max_leaf);
+}
+
+void BspRenderer::render_level(SharedRenderState* render_state,
+                               ScopedProfilerNode& prof,
+                               LevelCache* lc) {
+  auto shader = render_state->shaders[ShaderId::BSP].id();
+  render_state->shaders[ShaderId::BSP].activate();
+  glUniformMatrix4fv(glGetUniformLocation(shader, "camera"), 1, GL_FALSE,
+                     render_state->camera_matrix[0].data());
+  glUniform4f(glGetUniformLocation(shader, "hvdf_offset"), render_state->camera_hvdf_off[0],
+              render_state->camera_hvdf_off[1], render_state->camera_hvdf_off[2],
+              render_state->camera_hvdf_off[3]);
+  const auto& trans = render_state->camera_pos;
+  glUniform4f(glGetUniformLocation(shader, "camera_position"), trans[0], trans[1], trans[2],
+              trans[3]);
+  glUniform1f(glGetUniformLocation(shader, "fog_constant"), render_state->camera_fog.x());
+  glUniform1f(glGetUniformLocation(shader, "fog_min"), render_state->camera_fog.y());
+  glUniform1f(glGetUniformLocation(shader, "fog_max"), render_state->camera_fog.z());
+  glUniform1i(glGetUniformLocation(shader, "min_leaf"), (GLint)min_leaf);
+  glUniform1i(glGetUniformLocation(shader, "max_leaf"), (GLint)max_leaf);
+
+  glEnable(GL_DEPTH_TEST);
+  glDepthFunc(GL_GEQUAL);
+  glEnable(GL_BLEND);
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);  // ?
+  glDepthMask(GL_TRUE);
+
+  glBindBuffer(GL_ARRAY_BUFFER, lc->vertex_buffer);
+  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, lc->index_buffer);
+  glEnableVertexAttribArray(0);
+  glEnableVertexAttribArray(1);
+  glEnableVertexAttribArray(2);
+  glEnableVertexAttribArray(3);
+  glVertexAttribPointer(0,                             // location 0 in the shader
+                        3,                             // 3 values per vert
+                        GL_FLOAT,                      // floats
+                        GL_FALSE,                      // normalized
+                        sizeof(tfrag3::BspVisVertex),  // stride
+                        0                              // offset (0)
+  );
+  glVertexAttribIPointer(1,                             // location 1 in the shader
+                         1,                             // 3 values per vert
+                         GL_UNSIGNED_SHORT,             // u16
+                         sizeof(tfrag3::BspVisVertex),  // stride
+                         (void*)offsetof(tfrag3::BspVisVertex, bsp_cell)  // offset
+  );
+  glEnable(GL_PRIMITIVE_RESTART);
+  glPrimitiveRestartIndex(UINT32_MAX);
+  glUniform1i(glGetUniformLocation(shader, "wireframe"), 0);
+  // glDrawElements(GL_TRIANGLE_FAN, lc->index_count, GL_UNSIGNED_INT, nullptr);
+
+  if (true) {
+    glUniform1i(glGetUniformLocation(shader, "wireframe"), 1);
+    glDisable(GL_BLEND);
+    glDepthMask(GL_FALSE);
+    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+    glLineWidth(3.0);
+    glDrawElements(GL_TRIANGLE_FAN, lc->index_count, GL_UNSIGNED_INT, nullptr);
+    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+    glEnable(GL_BLEND);
+    glDepthMask(GL_TRUE);
+  }
+
+  prof.add_draw_call();
+  prof.add_tri(lc->index_count);  // not exactly, but who cares.
+}
\ No newline at end of file
diff --git a/game/graphics/opengl_renderer/BspRenderer.h b/game/graphics/opengl_renderer/BspRenderer.h
new file mode 100644
index 0000000000..77e2144167
--- /dev/null
+++ b/game/graphics/opengl_renderer/BspRenderer.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include "common/versions/versions.h"
+
+#include "game/graphics/opengl_renderer/BucketRenderer.h"
+
+class BspRenderer {
+public:
+  BspRenderer(GameVersion version);
+  void render(SharedRenderState* render_state, ScopedProfilerNode& prof);
+  void draw_debug_window();
+  ~BspRenderer();
+
+private:
+  int min_leaf = 0;
+  int max_leaf = UINT16_MAX;
+  struct LevelCache {
+    std::string name;
+    GLuint index_buffer = -1;
+    GLuint vertex_buffer = -1;
+    int index_count = 0;
+  };
+
+  void unload_cached_for_name(const std::string& name);
+  void load_level(LevelData* level, LevelCache* lc);
+  void unload_level(LevelCache* lc);
+  void render_level(SharedRenderState* render_state, ScopedProfilerNode& prof, LevelCache* lc);
+
+
+  std::map<uint64_t, LevelCache> m_level_cache;
+
+  GLuint m_vao;
+};
diff --git a/game/graphics/opengl_renderer/OpenGLRenderer.cpp b/game/graphics/opengl_renderer/OpenGLRenderer.cpp
index aeacfc1558..e868386228 100644
--- a/game/graphics/opengl_renderer/OpenGLRenderer.cpp
+++ b/game/graphics/opengl_renderer/OpenGLRenderer.cpp
@@ -74,6 +74,7 @@ OpenGLRenderer::OpenGLRenderer(std::shared_ptr<TexturePool> texture_pool,
                                GameVersion version)
     : m_render_state(texture_pool, loader, version),
       m_collide_renderer(version),
+      m_bsp_renderer(version),
       m_version(version) {
   // requires OpenGL 4.3
 #ifndef __APPLE__
@@ -1104,6 +1105,7 @@ void OpenGLRenderer::draw_renderer_selection_window() {
   ImGui::Checkbox("Sky CPU", &m_render_state.use_sky_cpu);
   ImGui::Checkbox("Occlusion Cull", &m_render_state.use_occlusion_culling);
   ImGui::Checkbox("Blackout Loads", &m_enable_fast_blackout_loads);
+  m_bsp_renderer.draw_debug_window();
 
   if (m_texture_animator && ImGui::TreeNode("Texture Animator")) {
     m_texture_animator->draw_debug_window();
@@ -1304,9 +1306,16 @@ void OpenGLRenderer::dispatch_buckets_jak1(DmaFollower dma,
     m_category_times[(int)m_bucket_categories[bucket_id]] += bucket_prof.get_elapsed_time();
 
     // hack to draw the collision mesh in the middle the drawing
-    if (bucket_id == 31 - 1 && Gfx::g_global_settings.collision_enable) {
-      auto p = prof.make_scoped_child("collision-draw");
-      m_collide_renderer.render(&m_render_state, p);
+    if (bucket_id == 31 - 1) {
+      if (Gfx::g_global_settings.collision_enable) {
+        auto p = prof.make_scoped_child("collision-draw");
+        m_collide_renderer.render(&m_render_state, p);
+      }
+
+      {
+        auto p = prof.make_scoped_child("bsp-draw");
+        m_bsp_renderer.render(&m_render_state, p);
+      }
     }
   }
 
diff --git a/game/graphics/opengl_renderer/OpenGLRenderer.h b/game/graphics/opengl_renderer/OpenGLRenderer.h
index 9f0faad591..36cff88213 100644
--- a/game/graphics/opengl_renderer/OpenGLRenderer.h
+++ b/game/graphics/opengl_renderer/OpenGLRenderer.h
@@ -5,6 +5,7 @@
 
 #include "common/dma/dma_chain_read.h"
 
+#include "game/graphics/opengl_renderer/BspRenderer.h"
 #include "game/graphics/opengl_renderer/BucketRenderer.h"
 #include "game/graphics/opengl_renderer/CollideMeshRenderer.h"
 #include "game/graphics/opengl_renderer/Fbo.h"
@@ -120,6 +121,7 @@ class OpenGLRenderer {
   std::array<float, (int)BucketCategory::MAX_CATEGORIES> m_category_times;
   FullScreenDraw m_blackout_renderer;
   CollideMeshRenderer m_collide_renderer;
+  BspRenderer m_bsp_renderer;
 
   float m_last_pmode_alp = 1.;
   bool m_enable_fast_blackout_loads = true;
diff --git a/game/graphics/opengl_renderer/Shader.cpp b/game/graphics/opengl_renderer/Shader.cpp
index 9850d6b624..8fd497e410 100644
--- a/game/graphics/opengl_renderer/Shader.cpp
+++ b/game/graphics/opengl_renderer/Shader.cpp
@@ -131,6 +131,7 @@ ShaderLibrary::ShaderLibrary(GameVersion version) {
   at(ShaderId::HFRAG) = {"hfrag", version};
   at(ShaderId::HFRAG_MONTAGE) = {"hfrag_montage", version};
   at(ShaderId::PLAIN_TEXTURE) = {"plain_texture", version};
+  at(ShaderId::BSP) = {"bsp", version};
 
   for (auto& shader : m_shaders) {
     ASSERT_MSG(shader.okay(), "error compiling shader");
diff --git a/game/graphics/opengl_renderer/Shader.h b/game/graphics/opengl_renderer/Shader.h
index 02769f9528..17af54ef75 100644
--- a/game/graphics/opengl_renderer/Shader.h
+++ b/game/graphics/opengl_renderer/Shader.h
@@ -64,6 +64,7 @@ enum class ShaderId {
   HFRAG = 37,
   HFRAG_MONTAGE = 38,
   PLAIN_TEXTURE = 39,
+  BSP = 40,
   MAX_SHADERS
 };
 
diff --git a/game/graphics/opengl_renderer/shaders/bsp.frag b/game/graphics/opengl_renderer/shaders/bsp.frag
new file mode 100644
index 0000000000..5c9ea5b9b6
--- /dev/null
+++ b/game/graphics/opengl_renderer/shaders/bsp.frag
@@ -0,0 +1,11 @@
+#version 410 core
+
+out vec4 color;
+
+in vec4 fragment_color;
+
+void main() {
+
+  if (fragment_color.a <= 0) discard;
+  color = fragment_color;
+}
diff --git a/game/graphics/opengl_renderer/shaders/bsp.vert b/game/graphics/opengl_renderer/shaders/bsp.vert
new file mode 100644
index 0000000000..4135515d7f
--- /dev/null
+++ b/game/graphics/opengl_renderer/shaders/bsp.vert
@@ -0,0 +1,61 @@
+#version 410 core
+
+layout (location = 0) in vec3 position_in;
+layout (location = 1) in uint bsp_cell;
+// layout (location = 2) in vec3 normal_in;
+// layout (location = 3) in uint pat;
+
+uniform vec4 hvdf_offset;
+uniform mat4 camera;
+uniform vec4 camera_position;
+uniform float fog_constant;
+uniform float fog_min;
+uniform float fog_max;
+uniform int wireframe;
+uniform int min_leaf;
+uniform int max_leaf;
+
+out vec4 fragment_color;
+
+void main() {
+  // Step 3, the camera transform
+  vec4 transformed = -camera[3].xyzw;
+  transformed += -camera[0] * position_in.x;
+  transformed += -camera[1] * position_in.y;
+  transformed += -camera[2] * position_in.z;
+
+  // compute Q
+  float Q = fog_constant / transformed[3];
+
+  // perspective divide!
+  transformed.xyz *= Q;
+
+  // offset
+  transformed.xyz += hvdf_offset.xyz;
+
+  // correct xy offset
+  transformed.xy -= (2048.);
+
+  // correct z scale
+  transformed.z /= (8388608);
+  transformed.z -= 1;
+
+  // correct xy scale
+  transformed.x /= (256);
+  transformed.y /= -(128);
+
+  // hack
+  transformed.xyz *= transformed.w;
+
+  gl_Position = transformed;
+  // scissoring area adjust
+  gl_Position.y *= SCISSOR_ADJUST * HEIGHT_SCALE;
+
+  //
+  fragment_color = vec4(0.12, 0.12, 0.12, 0.5);
+
+  if (bsp_cell < min_leaf || bsp_cell > max_leaf) {
+    fragment_color.a = 0;
+  }
+
+}