diff --git a/engine/joint/v4k.h b/engine/joint/v4k.h
index f3e0e9b..e09fc15 100644
--- a/engine/joint/v4k.h
+++ b/engine/joint/v4k.h
@@ -385267,11 +385267,66 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
         struct iqmmesh *mesh = &q->meshes[i];
-#if 1
+#if 0
         GLfloat *pos = verts[q->meshes[i].first_vertex].position;
         m->meshcenters[i] = vec3(pos[0], pos[1], pos[2]);
 #else
-        // for (int j = 0; j < )
+        int first_triangle = mesh->first_triangle;
+        int num_triangles = mesh->num_triangles;
+        int vertex_count = 0;
+        vec3 center = {0};
+        aabb box = {
+            .min = {FLT_MAX, FLT_MAX, FLT_MAX},
+            .max = {-FLT_MAX, -FLT_MAX, -FLT_MAX}
+        };
+        float max_distance_squared = 0.0f;
+        for (int j = first_triangle; j < num_triangles+first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            // calculate mesh center
+            for (int k = 0; k < 3; ++k) {
+                iqm_vertex *v = &verts[tri->vertex[k]];
+                GLfloat *pos = v->position;
+                center.x += pos[0];
+                center.y += pos[1];
+                center.z += pos[2];
+                vertex_count++;
+
+                // Update AABB
+                box.min.x = fminf(box.min.x, pos[0]);
+                box.min.y = fminf(box.min.y, pos[1]);
+                box.min.z = fminf(box.min.z, pos[2]);
+                box.max.x = fmaxf(box.max.x, pos[0]);
+                box.max.y = fmaxf(box.max.y, pos[1]);
+                box.max.z = fmaxf(box.max.z, pos[2]);
+            }
+        }
+
+        if (vertex_count) {
+            center.x /= vertex_count;
+            center.y /= vertex_count;
+            center.z /= vertex_count;
+        }
+
+        // Compute bounding sphere radius
+        for (int j = first_triangle; j < num_triangles + first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            for (int k = 0; k < 3; ++k) {
+                int vertex_index = tri->vertex[k];
+                GLfloat *pos = verts[vertex_index].position;
+
+                float dx = pos[0] - center.x;
+                float dy = pos[1] - center.y;
+                float dz = pos[2] - center.z;
+                float distance_squared = dx*dx + dy*dy + dz*dz;
+                max_distance_squared = fmaxf(max_distance_squared, distance_squared);
+            }
+        }
+
+        m->meshcenters[i] = center;
+        m->meshbounds[i] = box;
+        m->meshradii[i] = sqrtf(max_distance_squared);
 #endif
     }
 
@@ -385939,6 +385994,28 @@ void model_clear_frustum(model_t *m) {
     m->frustum_enabled = 0;
 }
 
+static inline
+bool model_is_visible(model_t m, int mesh, mat44 model_mat) {
+    if(!m.iqm) return false;
+    if(!m.frustum_enabled) return true;
+
+    sphere s; s.c = transform344(model_mat, m.meshcenters[mesh]); s.r = m.meshradii[mesh];
+
+    if (!frustum_test_sphere(m.frustum_state, s)) {
+        return false;
+    }
+
+    aabb box = m.meshbounds[mesh];
+    box.min = transform344(model_mat, box.min);
+    box.max = transform344(model_mat, box.max);
+
+    if (!frustum_test_aabb(m.frustum_state, box)) {
+        return false;
+    }
+
+    return true;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -385971,11 +386048,14 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
 
     if (rs_idx > RENDER_PASS_OVERRIDES_BEGIN) {
         for(int i = 0; i < q->nummeshes; i++) {
+            if (!model_is_visible(m, i, model_mat)) continue;
             array_push(drawcalls, (drawcall_t){i, -1});
         }
     } else {
         if(pass == -1 || pass == RENDER_PASS_OPAQUE) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect opaque drawcalls
                 if (required_rs[i] == RENDER_PASS_OPAQUE) {
                     drawcall_t call;
@@ -385991,6 +386071,8 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         
         if(pass == -1 || pass == RENDER_PASS_TRANSPARENT) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect transparent drawcalls
                 if (required_rs[i] == RENDER_PASS_TRANSPARENT) {
                     drawcall_t call;
@@ -388087,8 +388169,22 @@ int scene_obj_distance_compare(const void *a, const void *b) {
 
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+
+#if 1
     mat44 projview; multiply44x2(projview, cam->proj, cam->view);
     frustum frustum_state = frustum_build(projview);
+#else
+    static frustum frustum_state;
+    do_once {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+
+    if (input_down(KEY_T)) {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+#endif
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {
diff --git a/engine/split/v4k_render.c b/engine/split/v4k_render.c
index e705ac4..3c33412 100644
--- a/engine/split/v4k_render.c
+++ b/engine/split/v4k_render.c
@@ -3611,11 +3611,66 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
         struct iqmmesh *mesh = &q->meshes[i];
-#if 1
+#if 0
         GLfloat *pos = verts[q->meshes[i].first_vertex].position;
         m->meshcenters[i] = vec3(pos[0], pos[1], pos[2]);
 #else
-        // for (int j = 0; j < )
+        int first_triangle = mesh->first_triangle;
+        int num_triangles = mesh->num_triangles;
+        int vertex_count = 0;
+        vec3 center = {0};
+        aabb box = {
+            .min = {FLT_MAX, FLT_MAX, FLT_MAX},
+            .max = {-FLT_MAX, -FLT_MAX, -FLT_MAX}
+        };
+        float max_distance_squared = 0.0f;
+        for (int j = first_triangle; j < num_triangles+first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            // calculate mesh center
+            for (int k = 0; k < 3; ++k) {
+                iqm_vertex *v = &verts[tri->vertex[k]];
+                GLfloat *pos = v->position;
+                center.x += pos[0];
+                center.y += pos[1];
+                center.z += pos[2];
+                vertex_count++;
+
+                // Update AABB
+                box.min.x = fminf(box.min.x, pos[0]);
+                box.min.y = fminf(box.min.y, pos[1]);
+                box.min.z = fminf(box.min.z, pos[2]);
+                box.max.x = fmaxf(box.max.x, pos[0]);
+                box.max.y = fmaxf(box.max.y, pos[1]);
+                box.max.z = fmaxf(box.max.z, pos[2]);
+            }
+        }
+
+        if (vertex_count) {
+            center.x /= vertex_count;
+            center.y /= vertex_count;
+            center.z /= vertex_count;
+        }
+
+        // Compute bounding sphere radius
+        for (int j = first_triangle; j < num_triangles + first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            for (int k = 0; k < 3; ++k) {
+                int vertex_index = tri->vertex[k];
+                GLfloat *pos = verts[vertex_index].position;
+
+                float dx = pos[0] - center.x;
+                float dy = pos[1] - center.y;
+                float dz = pos[2] - center.z;
+                float distance_squared = dx*dx + dy*dy + dz*dz;
+                max_distance_squared = fmaxf(max_distance_squared, distance_squared);
+            }
+        }
+
+        m->meshcenters[i] = center;
+        m->meshbounds[i] = box;
+        m->meshradii[i] = sqrtf(max_distance_squared);
 #endif
     }
 
@@ -4283,6 +4338,28 @@ void model_clear_frustum(model_t *m) {
     m->frustum_enabled = 0;
 }
 
+static inline
+bool model_is_visible(model_t m, int mesh, mat44 model_mat) {
+    if(!m.iqm) return false;
+    if(!m.frustum_enabled) return true;
+
+    sphere s; s.c = transform344(model_mat, m.meshcenters[mesh]); s.r = m.meshradii[mesh];
+
+    if (!frustum_test_sphere(m.frustum_state, s)) {
+        return false;
+    }
+
+    aabb box = m.meshbounds[mesh];
+    box.min = transform344(model_mat, box.min);
+    box.max = transform344(model_mat, box.max);
+
+    if (!frustum_test_aabb(m.frustum_state, box)) {
+        return false;
+    }
+
+    return true;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -4315,11 +4392,14 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
 
     if (rs_idx > RENDER_PASS_OVERRIDES_BEGIN) {
         for(int i = 0; i < q->nummeshes; i++) {
+            if (!model_is_visible(m, i, model_mat)) continue;
             array_push(drawcalls, (drawcall_t){i, -1});
         }
     } else {
         if(pass == -1 || pass == RENDER_PASS_OPAQUE) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect opaque drawcalls
                 if (required_rs[i] == RENDER_PASS_OPAQUE) {
                     drawcall_t call;
@@ -4335,6 +4415,8 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         
         if(pass == -1 || pass == RENDER_PASS_TRANSPARENT) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect transparent drawcalls
                 if (required_rs[i] == RENDER_PASS_TRANSPARENT) {
                     drawcall_t call;
diff --git a/engine/split/v4k_scene.c b/engine/split/v4k_scene.c
index f2d6158..91e01f4 100644
--- a/engine/split/v4k_scene.c
+++ b/engine/split/v4k_scene.c
@@ -513,8 +513,22 @@ int scene_obj_distance_compare(const void *a, const void *b) {
 
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+
+#if 1
     mat44 projview; multiply44x2(projview, cam->proj, cam->view);
     frustum frustum_state = frustum_build(projview);
+#else
+    static frustum frustum_state;
+    do_once {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+
+    if (input_down(KEY_T)) {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+#endif
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {
diff --git a/engine/v4k.c b/engine/v4k.c
index 28215fd..9a52fa4 100644
--- a/engine/v4k.c
+++ b/engine/v4k.c
@@ -20410,11 +20410,66 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
         struct iqmmesh *mesh = &q->meshes[i];
-#if 1
+#if 0
         GLfloat *pos = verts[q->meshes[i].first_vertex].position;
         m->meshcenters[i] = vec3(pos[0], pos[1], pos[2]);
 #else
-        // for (int j = 0; j < )
+        int first_triangle = mesh->first_triangle;
+        int num_triangles = mesh->num_triangles;
+        int vertex_count = 0;
+        vec3 center = {0};
+        aabb box = {
+            .min = {FLT_MAX, FLT_MAX, FLT_MAX},
+            .max = {-FLT_MAX, -FLT_MAX, -FLT_MAX}
+        };
+        float max_distance_squared = 0.0f;
+        for (int j = first_triangle; j < num_triangles+first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            // calculate mesh center
+            for (int k = 0; k < 3; ++k) {
+                iqm_vertex *v = &verts[tri->vertex[k]];
+                GLfloat *pos = v->position;
+                center.x += pos[0];
+                center.y += pos[1];
+                center.z += pos[2];
+                vertex_count++;
+
+                // Update AABB
+                box.min.x = fminf(box.min.x, pos[0]);
+                box.min.y = fminf(box.min.y, pos[1]);
+                box.min.z = fminf(box.min.z, pos[2]);
+                box.max.x = fmaxf(box.max.x, pos[0]);
+                box.max.y = fmaxf(box.max.y, pos[1]);
+                box.max.z = fmaxf(box.max.z, pos[2]);
+            }
+        }
+
+        if (vertex_count) {
+            center.x /= vertex_count;
+            center.y /= vertex_count;
+            center.z /= vertex_count;
+        }
+
+        // Compute bounding sphere radius
+        for (int j = first_triangle; j < num_triangles + first_triangle; ++j) {
+            struct iqmtriangle *tri = &tris[j];
+
+            for (int k = 0; k < 3; ++k) {
+                int vertex_index = tri->vertex[k];
+                GLfloat *pos = verts[vertex_index].position;
+
+                float dx = pos[0] - center.x;
+                float dy = pos[1] - center.y;
+                float dz = pos[2] - center.z;
+                float distance_squared = dx*dx + dy*dy + dz*dz;
+                max_distance_squared = fmaxf(max_distance_squared, distance_squared);
+            }
+        }
+
+        m->meshcenters[i] = center;
+        m->meshbounds[i] = box;
+        m->meshradii[i] = sqrtf(max_distance_squared);
 #endif
     }
 
@@ -21082,6 +21137,28 @@ void model_clear_frustum(model_t *m) {
     m->frustum_enabled = 0;
 }
 
+static inline
+bool model_is_visible(model_t m, int mesh, mat44 model_mat) {
+    if(!m.iqm) return false;
+    if(!m.frustum_enabled) return true;
+
+    sphere s; s.c = transform344(model_mat, m.meshcenters[mesh]); s.r = m.meshradii[mesh];
+
+    if (!frustum_test_sphere(m.frustum_state, s)) {
+        return false;
+    }
+
+    aabb box = m.meshbounds[mesh];
+    box.min = transform344(model_mat, box.min);
+    box.max = transform344(model_mat, box.max);
+
+    if (!frustum_test_aabb(m.frustum_state, box)) {
+        return false;
+    }
+
+    return true;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -21114,11 +21191,14 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
 
     if (rs_idx > RENDER_PASS_OVERRIDES_BEGIN) {
         for(int i = 0; i < q->nummeshes; i++) {
+            if (!model_is_visible(m, i, model_mat)) continue;
             array_push(drawcalls, (drawcall_t){i, -1});
         }
     } else {
         if(pass == -1 || pass == RENDER_PASS_OPAQUE) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect opaque drawcalls
                 if (required_rs[i] == RENDER_PASS_OPAQUE) {
                     drawcall_t call;
@@ -21134,6 +21214,8 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         
         if(pass == -1 || pass == RENDER_PASS_TRANSPARENT) {
             for(int i = 0; i < q->nummeshes; i++) {
+                if (!model_is_visible(m, i, model_mat)) continue;
+
                 // collect transparent drawcalls
                 if (required_rs[i] == RENDER_PASS_TRANSPARENT) {
                     drawcall_t call;
@@ -23230,8 +23312,22 @@ int scene_obj_distance_compare(const void *a, const void *b) {
 
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+
+#if 1
     mat44 projview; multiply44x2(projview, cam->proj, cam->view);
     frustum frustum_state = frustum_build(projview);
+#else
+    static frustum frustum_state;
+    do_once {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+
+    if (input_down(KEY_T)) {
+        mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+        frustum_state = frustum_build(projview);
+    }
+#endif
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {