diff --git a/bind/v4k.lua b/bind/v4k.lua
index 184ecf8..309983b 100644
--- a/bind/v4k.lua
+++ b/bind/v4k.lua
@@ -1387,6 +1387,8 @@ typedef struct model_t {
     int num_verts;
     void *tris;
     vec3 *meshcenters;
+    aabb *meshbounds;
+    float *meshradii;
     int num_tris;
     handle vao, ibo, vbo, vao_instanced;
     int* lod_collapse_map;
@@ -1400,6 +1402,8 @@ typedef struct model_t {
     unsigned num_instances;
     int stored_flags;
     renderstate_t rs[NUM_RENDER_PASSES];
+    bool frustum_enabled;
+    frustum frustum_state;
 } model_t;
 enum BILLBOARD_MODE {
     BILLBOARD_X = 0x1,
@@ -1423,6 +1427,10 @@ enum BILLBOARD_MODE {
  void model_render_instanced_pass(model_t m, mat44 proj, mat44 view, mat44* models, int shader, unsigned count, int pass);
  void model_render_pass(model_t m, mat44 proj, mat44 view, mat44 model, int shader, int pass);
  void model_set_texture(model_t*, texture_t t);
+ bool model_has_transparency_mesh(model_t m, int mesh);
+ bool model_has_transparency(model_t m);
+ void model_set_frustum(model_t *m, frustum f);
+ void model_clear_frustum(model_t *m);
  bool model_get_bone_pose(model_t m, unsigned joint, mat34 *out);
  void model_destroy(model_t);
  unsigned model_getpass();
@@ -1555,6 +1563,11 @@ typedef struct object_t {
     float anim_speed;
     aabb bounds;
     unsigned billboard;
+    bool disable_frustum_check;
+    handle* old_texture_ids;
+    texture_t* old_textures;
+    float distance;
+    bool skip_draw;
     bool light_cached;
 } object_t;
  object_t object();
diff --git a/demos/06-scene-sorting.c b/demos/06-scene-sorting.c
new file mode 100644
index 0000000..55901e2
--- /dev/null
+++ b/demos/06-scene-sorting.c
@@ -0,0 +1,58 @@
+// render map
+
+#include "v4k.h"
+
+int main() {
+    window_create(80, WINDOW_MSAA8);
+    window_title(__FILE__);
+    window_fps_unlock();
+
+    // load skybox
+    skybox_t sky = skybox("bridge3", 0); 
+
+    // load static scene
+    model_t map, prop;
+    map = model(option("--model","sorting_test.obj"), 0); // MODEL_NO_TEXTURES);
+    prop = model(option("--model","sorting_test2.obj"), 0); // MODEL_NO_TEXTURES);
+    shader_bind(map.program);
+    skybox_sh_shader(&sky);
+    prop.program = map.program;
+
+    // define scene
+    object_t *prop_obj = scene_spawn();
+    object_model(prop_obj, prop);
+
+    object_t *map_obj = scene_spawn();
+    object_model(map_obj, map);
+
+    // camera
+    camera_t cam = camera();
+    cam.speed *= 0.05f;
+
+    // demo loop
+    while (window_swap())
+    {
+        // input
+        if( input_down(KEY_ESC) ) break;
+        if( input_down(KEY_F5) ) window_reload();
+        if( input_down(KEY_F11) ) window_fullscreen( window_has_fullscreen() ^ 1 );
+        if( input_down(KEY_X) ) window_screenshot(__FILE__ ".png");
+        if( input_down(KEY_Z) ) window_record(__FILE__ ".mp4");
+
+        // fps camera
+        bool active = ui_active() || ui_hover() || gizmo_active() ? false : input(MOUSE_L) || input(MOUSE_M) || input(MOUSE_R);
+        if( active ) cam.speed = clampf(cam.speed + input_diff(MOUSE_W) / 10, 0.05f, 5.0f);
+        vec2 mouse = scale2(vec2(input_diff(MOUSE_X), -input_diff(MOUSE_Y)), 0.2f * active);
+        vec3 wasdecq = scale3(vec3(input(KEY_D)-input(KEY_A),input(KEY_E)-(input(KEY_C)||input(KEY_Q)),input(KEY_W)-input(KEY_S)), cam.speed);
+        camera_moveby(&cam, wasdecq);
+        camera_fps(&cam, mouse.x,mouse.y);
+        window_cursor( !active );
+
+        // draw skybox
+        profile("Skybox") {
+            skybox_render(&sky, cam.proj, cam.view);
+        }
+
+        scene_render(SCENE_FOREGROUND);
+    }
+}
diff --git a/demos/06-sorting.c b/demos/06-sorting.c
index 44144e6..1848b79 100644
--- a/demos/06-sorting.c
+++ b/demos/06-sorting.c
@@ -7,21 +7,14 @@ int main() {
     window_title(__FILE__);
     window_fps_unlock();
 
-    // load all fx files
-    fx_load("fx**.fs");
-
     // load skybox
-    // skybox_t sky = skybox(flag("--mie") ? 0 : "hdr/Tokyo_BigSight_1k.hdr", 0); // --mie for rayleigh/mie scattering
-    skybox_t sky = skybox("bridge3", 0); // --mie for rayleigh/mie scattering
+    skybox_t sky = skybox("bridge3", 0); 
 
     // load static scene
     model_t map;
     map = model(option("--model","sorting_test.obj"), 0); // MODEL_NO_TEXTURES);
     shader_bind(map.program);
     skybox_sh_shader(&sky);
-    // translation44(map.pivot, 0,-1,0);
-    // rotate44(map.pivot, -90,1,0,0);
-    // scale44(map.pivot, 10,10,10);
 
     // camera
     camera_t cam = camera();
@@ -53,12 +46,6 @@ int main() {
 
         mat44 M; copy44(M, map.pivot);// translate44(M, 0,0,0); scale44(M, scale,scale,scale);
 
-        // apply post-fxs from here
-        fx_begin();
-
-        model_render_pass(map, cam.proj, cam.view, M, 0, -1);
-
-        // post-fxs end here
-        fx_end(0);
+        model_render(map, cam.proj, cam.view, M, 0);
     }
 }
diff --git a/demos/art/meshes/sorting_test2.mtl b/demos/art/meshes/sorting_test2.mtl
new file mode 100644
index 0000000..66e6861
--- /dev/null
+++ b/demos/art/meshes/sorting_test2.mtl
@@ -0,0 +1,52 @@
+# Blender 4.2.1 LTS MTL File: 'None'
+# www.blender.org
+
+newmtl Material.006
+Ns 250.000000
+Ka 1.000000 1.000000 1.000000
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.500000
+d 1.000000
+illum 2
+map_Kd E:/v4games/v4k/demos/art/matcaps/material3.jpg
+
+newmtl Material.007
+Ns 250.000000
+Ka 1.000000 1.000000 1.000000
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.450000
+d 1.000000
+illum 2
+map_Kd E:/v4games/v4k/demos/art/matcaps/test_steel.jpg
+
+newmtl Material.008
+Ns 250.000000
+Ka 1.000000 1.000000 1.000000
+Kd 0.059941 0.801453 0.027650
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.500000
+d 0.228070
+illum 9
+
+newmtl Material.009
+Ns 250.000000
+Ka 1.000000 1.000000 1.000000
+Kd 0.015818 0.013069 0.801024
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.500000
+d 0.294737
+illum 9
+
+newmtl Material.010
+Ns 250.000000
+Ka 1.000000 1.000000 1.000000
+Kd 0.800063 0.776954 0.209224
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.500000
+d 0.480702
+illum 9
diff --git a/demos/art/meshes/sorting_test2.obj b/demos/art/meshes/sorting_test2.obj
new file mode 100644
index 0000000..e40f0ed
--- /dev/null
+++ b/demos/art/meshes/sorting_test2.obj
@@ -0,0 +1,70 @@
+# Blender 4.2.1 LTS
+# www.blender.org
+mtllib sorting_test2.mtl
+o Cube.001
+v 6.691334 -10.979122 -7.520660
+v 6.691334 -10.979120 -11.912354
+v -6.691334 -10.979122 -7.520660
+v -6.691334 -10.979120 -11.912354
+v 6.691333 -15.370816 -7.520660
+v 6.691333 -15.370816 -11.912354
+v -6.691335 -15.370814 -7.520660
+v -6.691335 -15.370814 -11.912354
+v 6.691334 -1.734141 -7.520659
+v 6.691334 -1.734141 -11.912354
+v -6.691334 -1.734140 -7.520659
+v -6.691334 -1.734140 -11.912354
+v 6.691334 -6.125834 -7.520660
+v 6.691334 -6.125834 -11.912353
+v -6.691333 -6.125834 -7.520660
+v -6.691333 -6.125834 -11.912353
+v 6.691335 6.836245 -7.520658
+v 6.691335 6.836244 -11.912353
+v -6.691332 6.836244 -7.520658
+v -6.691332 6.836243 -11.912353
+v 6.691335 2.444547 -7.520658
+v 6.691335 2.444549 -11.912353
+v -6.691333 2.444548 -7.520658
+v -6.691333 2.444550 -11.912353
+vn -0.0000 1.0000 -0.0000
+vn -1.0000 -0.0000 -0.0000
+vn -0.0000 -1.0000 -0.0000
+vn 1.0000 -0.0000 -0.0000
+vn -0.0000 -0.0000 1.0000
+vn -0.0000 -0.0000 -1.0000
+vt 0.375000 0.000000
+vt 0.625000 0.000000
+vt 0.625000 0.250000
+vt 0.375000 0.250000
+vt 0.625000 0.500000
+vt 0.375000 0.500000
+vt 0.625000 0.750000
+vt 0.375000 0.750000
+vt 0.625000 1.000000
+vt 0.375000 1.000000
+vt 0.125000 0.500000
+vt 0.125000 0.750000
+vt 0.875000 0.500000
+vt 0.875000 0.750000
+s 0
+usemtl Material.008
+f 1/1/1 2/2/1 4/3/1 3/4/1
+f 3/4/2 4/3/2 8/5/2 7/6/2
+f 7/6/3 8/5/3 6/7/3 5/8/3
+f 5/8/4 6/7/4 2/9/4 1/10/4
+f 3/11/5 7/6/5 5/8/5 1/12/5
+f 8/5/6 4/13/6 2/14/6 6/7/6
+usemtl Material.009
+f 9/1/1 10/2/1 12/3/1 11/4/1
+f 11/4/2 12/3/2 16/5/2 15/6/2
+f 15/6/3 16/5/3 14/7/3 13/8/3
+f 13/8/4 14/7/4 10/9/4 9/10/4
+f 11/11/5 15/6/5 13/8/5 9/12/5
+f 16/5/6 12/13/6 10/14/6 14/7/6
+usemtl Material.010
+f 17/1/1 18/2/1 20/3/1 19/4/1
+f 19/4/2 20/3/2 24/5/2 23/6/2
+f 23/6/3 24/5/3 22/7/3 21/8/3
+f 21/8/4 22/7/4 18/9/4 17/10/4
+f 19/11/5 23/6/5 21/8/5 17/12/5
+f 24/5/6 20/13/6 18/14/6 22/7/6
diff --git a/engine/joint/v4k.h b/engine/joint/v4k.h
index 3cda235..f3e0e9b 100644
--- a/engine/joint/v4k.h
+++ b/engine/joint/v4k.h
@@ -17645,6 +17645,8 @@ typedef struct model_t {
     int num_verts;
     void *tris;
     vec3 *meshcenters;
+    aabb *meshbounds;
+    float *meshradii;
     int num_tris;
     handle vao, ibo, vbo, vao_instanced;
 
@@ -17662,6 +17664,9 @@ typedef struct model_t {
 
     int stored_flags;
     renderstate_t rs[NUM_RENDER_PASSES];
+
+    bool frustum_enabled;
+    frustum frustum_state;
 } model_t;
 
 enum BILLBOARD_MODE {
@@ -17688,6 +17693,10 @@ API void     model_render_instanced(model_t, mat44 proj, mat44 view, mat44 *mode
 API void     model_render_instanced_pass(model_t m, mat44 proj, mat44 view, mat44* models, int shader, unsigned count, int pass);
 API void     model_render_pass(model_t m, mat44 proj, mat44 view, mat44 model, int shader, int pass);
 API void     model_set_texture(model_t*, texture_t t);
+API bool     model_has_transparency_mesh(model_t m, int mesh);
+API bool     model_has_transparency(model_t m);
+API void     model_set_frustum(model_t *m, frustum f);
+API void     model_clear_frustum(model_t *m);
 API bool     model_get_bone_pose(model_t m, unsigned joint, mat34 *out);
 API void     model_destroy(model_t);
 
@@ -17884,6 +17893,13 @@ typedef struct object_t {
     float anim_speed;
     aabb bounds;
     unsigned billboard; // [0..7] x(4),y(2),z(1) masks
+    bool disable_frustum_check;
+
+    // internal states
+    array(handle) old_texture_ids;
+    array(texture_t) old_textures;
+    float distance;
+    bool skip_draw;
     bool light_cached; //< used by scene to update light data
 } object_t;
 
@@ -385244,12 +385260,19 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
     q->textures = CALLOC(hdr->num_meshes * 8, sizeof(GLuint));
     q->colormaps = CALLOC(hdr->num_meshes * 8, sizeof(vec4));
     m->meshcenters = CALLOC(hdr->num_meshes, sizeof(vec3));
+    m->meshbounds = CALLOC(hdr->num_meshes, sizeof(aabb));
+    m->meshradii = CALLOC(hdr->num_meshes, sizeof(float));
 
     for(int i = 0; i < (int)hdr->num_meshes; i++) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
+        struct iqmmesh *mesh = &q->meshes[i];
+#if 1
         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 < )
+#endif
     }
 
     const char *str = hdr->ofs_text ? (char *)&q->buf[hdr->ofs_text] : "";
@@ -385876,6 +385899,46 @@ int drawcall_compare(const void *a, const void *b) {
     return da->order < db->order ? 1 : da->order > db->order ? -1 : 0;
 }
 
+bool model_has_transparency_mesh(model_t m, int mesh) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    if (m.flags & MODEL_TRANSPARENT) {
+        return true;
+    }
+    if (m.materials[mesh].layer[0].map.color.a < 1 || (m.materials[mesh].layer[0].map.texture && m.materials[mesh].layer[0].map.texture->transparent)) {
+        return true;
+    }
+    if (m.shading == SHADING_PBR && (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+        return true;
+    }
+
+    return false;
+}
+
+bool model_has_transparency(model_t m) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    for (int i = 0; i < q->nummeshes; i++) {
+        if (model_has_transparency_mesh(m, i)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+
+void model_set_frustum(model_t *m, frustum f) {
+    m->frustum_enabled = 1;
+    m->frustum_state = f;
+}
+
+void model_clear_frustum(model_t *m) {
+    m->frustum_enabled = 0;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -385897,13 +385960,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         required_rs[i] = rs_idx;
 
         if (required_rs[i] < RENDER_PASS_OVERRIDES_BEGIN) {
-            if (m.flags & MODEL_TRANSPARENT) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.materials[i].layer[0].map.color.a < 1 || (m.materials[i].layer[0].map.texture && m.materials[i].layer[0].map.texture->transparent)) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.shading == SHADING_PBR && (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+            if (model_has_transparency_mesh(m, i)) {
                 required_rs[i] = RENDER_PASS_TRANSPARENT;
             }
         }
@@ -385943,7 +386000,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
                     // calculate distance from camera
                     // @todo: improve me, uses first mesh triangle
                     {
-                        call.distance = len3(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
+                        call.distance = len3sq(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
                     }
 
                     if (m.shading == SHADING_PBR)
@@ -386372,6 +386429,8 @@ void model_destroy(model_t m) {
     }
     array_free(m.texture_names);
     FREE(m.meshcenters);
+    FREE(m.meshbounds);
+    FREE(m.meshradii);
 
     iqm_t *q = m.iqm;
 //    if(m.mesh) mesh_destroy(m.mesh);
@@ -388020,8 +388079,16 @@ light_t* scene_index_light(unsigned light_index) {
     return &last_scene->lights[light_index];
 }
 
+static
+int scene_obj_distance_compare(const void *a, const void *b) {
+    const object_t *da = a, *db = b;
+    return da->distance < db->distance ? 1 : da->distance > db->distance ? -1 : 0;
+}
+
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+    mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+    frustum frustum_state = frustum_build(projview);
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {
@@ -388047,18 +388114,18 @@ void scene_render(int flags) {
             model_t *model = &obj->model;
             anim_t *anim = &obj->anim;
             mat44 *views = (mat44*)(&cam->view);
+            
+            obj->skip_draw = !obj->disable_frustum_check && !frustum_test_aabb(frustum_state, model_aabb(*model, obj->transform));
 
-            // @todo: avoid heap allocs here?
-            static array(handle) old_texture_ids = 0;
-            static array(texture_t) old_textures = 0;
+            if (obj->skip_draw) continue;
 
             int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    array_push(old_texture_ids, model->iqm->textures[i]);
+                    array_push(obj->old_texture_ids, model->iqm->textures[i]);
                     model->iqm->textures[i] = (*array_back(obj->textures)).id;
                     if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture) {
-                        array_push(old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
+                        array_push(obj->old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
                         *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = (*array_back(obj->textures));
                     }
                 }
@@ -388072,32 +388139,80 @@ void scene_render(int flags) {
 
             if ( flags&SCENE_UPDATE_SH_COEF ) {
                 shader_bind(model->program);
-                shader_vec3v("u_coefficients_sh", 9, last_scene->skybox.cubemap.sh);
+                skybox_sh_shader(&last_scene->skybox);
             }
-     
+
             model_skybox(model, last_scene->skybox, 0);
 
+            if (!obj->disable_frustum_check)
+                model_set_frustum(model, frustum_state);
+            else
+                model_clear_frustum(model);
+
             if (anim) {
                 float delta = window_delta() * obj->anim_speed;
                 model->curframe = model_animate_clip(*model, model->curframe + delta, anim->from, anim->to, anim->flags & ANIM_LOOP );
             }
 
-
             model->billboard = obj->billboard;
-            model->rs[RENDER_PASS_OPAQUE].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
-            model->rs[RENDER_PASS_OPAQUE].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
-            model_render(*model, cam->proj, cam->view, obj->transform, model->program);
+            for (int p = 0; p < RENDER_PASS_OVERRIDES_BEGIN; ++p) {
+                model->rs[p].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
+                model->rs[p].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
+            }
+        }
+        
+        /* Collect all transparency enabled models and sort them by distance */
+        static array(object_t*) transparent_objects = 0;
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
 
+            if (obj->skip_draw) continue;
+
+            if (model_has_transparency(*model)) {
+                obj->distance = len3sq(sub3(cam->position, transform344(model->pivot, add3(obj->pos, model->meshcenters[0]))));
+                array_push(transparent_objects, obj);
+            }
+        }
+
+        array_sort(transparent_objects, scene_obj_distance_compare);
+
+        /* Opaque pass */
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_OPAQUE);
+        }
+
+        /* Transparency pass */
+        for (unsigned j = 0; j < array_count(transparent_objects); ++j) {
+            object_t *obj = transparent_objects[j];
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_TRANSPARENT);
+        }
+
+        array_resize(transparent_objects, 0);
+
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    model->iqm->textures[i] = old_texture_ids[i];
-                    if (i < array_count(old_textures)) {
+                    model->iqm->textures[i] = obj->old_texture_ids[i];
+                    if (i < array_count(obj->old_textures)) {
                         if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture)
-                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = old_textures[i];
+                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = obj->old_textures[i];
                     }
                 }
-                array_resize(old_texture_ids, 0);
-                array_resize(old_textures, 0);
+                array_resize(obj->old_texture_ids, 0);
+                array_resize(obj->old_textures, 0);
             }
         }
         glBindVertexArray(0);
diff --git a/engine/split/v4k_render.c b/engine/split/v4k_render.c
index 6de2093..e705ac4 100644
--- a/engine/split/v4k_render.c
+++ b/engine/split/v4k_render.c
@@ -3604,12 +3604,19 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
     q->textures = CALLOC(hdr->num_meshes * 8, sizeof(GLuint));
     q->colormaps = CALLOC(hdr->num_meshes * 8, sizeof(vec4));
     m->meshcenters = CALLOC(hdr->num_meshes, sizeof(vec3));
+    m->meshbounds = CALLOC(hdr->num_meshes, sizeof(aabb));
+    m->meshradii = CALLOC(hdr->num_meshes, sizeof(float));
 
     for(int i = 0; i < (int)hdr->num_meshes; i++) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
+        struct iqmmesh *mesh = &q->meshes[i];
+#if 1
         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 < )
+#endif
     }
 
     const char *str = hdr->ofs_text ? (char *)&q->buf[hdr->ofs_text] : "";
@@ -4236,6 +4243,46 @@ int drawcall_compare(const void *a, const void *b) {
     return da->order < db->order ? 1 : da->order > db->order ? -1 : 0;
 }
 
+bool model_has_transparency_mesh(model_t m, int mesh) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    if (m.flags & MODEL_TRANSPARENT) {
+        return true;
+    }
+    if (m.materials[mesh].layer[0].map.color.a < 1 || (m.materials[mesh].layer[0].map.texture && m.materials[mesh].layer[0].map.texture->transparent)) {
+        return true;
+    }
+    if (m.shading == SHADING_PBR && (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+        return true;
+    }
+
+    return false;
+}
+
+bool model_has_transparency(model_t m) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    for (int i = 0; i < q->nummeshes; i++) {
+        if (model_has_transparency_mesh(m, i)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+
+void model_set_frustum(model_t *m, frustum f) {
+    m->frustum_enabled = 1;
+    m->frustum_state = f;
+}
+
+void model_clear_frustum(model_t *m) {
+    m->frustum_enabled = 0;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -4257,13 +4304,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         required_rs[i] = rs_idx;
 
         if (required_rs[i] < RENDER_PASS_OVERRIDES_BEGIN) {
-            if (m.flags & MODEL_TRANSPARENT) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.materials[i].layer[0].map.color.a < 1 || (m.materials[i].layer[0].map.texture && m.materials[i].layer[0].map.texture->transparent)) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.shading == SHADING_PBR && (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+            if (model_has_transparency_mesh(m, i)) {
                 required_rs[i] = RENDER_PASS_TRANSPARENT;
             }
         }
@@ -4303,7 +4344,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
                     // calculate distance from camera
                     // @todo: improve me, uses first mesh triangle
                     {
-                        call.distance = len3(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
+                        call.distance = len3sq(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
                     }
 
                     if (m.shading == SHADING_PBR)
@@ -4732,6 +4773,8 @@ void model_destroy(model_t m) {
     }
     array_free(m.texture_names);
     FREE(m.meshcenters);
+    FREE(m.meshbounds);
+    FREE(m.meshradii);
 
     iqm_t *q = m.iqm;
 //    if(m.mesh) mesh_destroy(m.mesh);
diff --git a/engine/split/v4k_render.h b/engine/split/v4k_render.h
index 992f785..96b1a03 100644
--- a/engine/split/v4k_render.h
+++ b/engine/split/v4k_render.h
@@ -677,6 +677,8 @@ typedef struct model_t {
     int num_verts;
     void *tris;
     vec3 *meshcenters;
+    aabb *meshbounds;
+    float *meshradii;
     int num_tris;
     handle vao, ibo, vbo, vao_instanced;
 
@@ -694,6 +696,9 @@ typedef struct model_t {
 
     int stored_flags;
     renderstate_t rs[NUM_RENDER_PASSES];
+
+    bool frustum_enabled;
+    frustum frustum_state;
 } model_t;
 
 enum BILLBOARD_MODE {
@@ -720,6 +725,10 @@ API void     model_render_instanced(model_t, mat44 proj, mat44 view, mat44 *mode
 API void     model_render_instanced_pass(model_t m, mat44 proj, mat44 view, mat44* models, int shader, unsigned count, int pass);
 API void     model_render_pass(model_t m, mat44 proj, mat44 view, mat44 model, int shader, int pass);
 API void     model_set_texture(model_t*, texture_t t);
+API bool     model_has_transparency_mesh(model_t m, int mesh);
+API bool     model_has_transparency(model_t m);
+API void     model_set_frustum(model_t *m, frustum f);
+API void     model_clear_frustum(model_t *m);
 API bool     model_get_bone_pose(model_t m, unsigned joint, mat34 *out);
 API void     model_destroy(model_t);
 
diff --git a/engine/split/v4k_scene.c b/engine/split/v4k_scene.c
index bc821eb..f2d6158 100644
--- a/engine/split/v4k_scene.c
+++ b/engine/split/v4k_scene.c
@@ -505,8 +505,16 @@ light_t* scene_index_light(unsigned light_index) {
     return &last_scene->lights[light_index];
 }
 
+static
+int scene_obj_distance_compare(const void *a, const void *b) {
+    const object_t *da = a, *db = b;
+    return da->distance < db->distance ? 1 : da->distance > db->distance ? -1 : 0;
+}
+
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+    mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+    frustum frustum_state = frustum_build(projview);
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {
@@ -532,18 +540,18 @@ void scene_render(int flags) {
             model_t *model = &obj->model;
             anim_t *anim = &obj->anim;
             mat44 *views = (mat44*)(&cam->view);
+            
+            obj->skip_draw = !obj->disable_frustum_check && !frustum_test_aabb(frustum_state, model_aabb(*model, obj->transform));
 
-            // @todo: avoid heap allocs here?
-            static array(handle) old_texture_ids = 0;
-            static array(texture_t) old_textures = 0;
+            if (obj->skip_draw) continue;
 
             int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    array_push(old_texture_ids, model->iqm->textures[i]);
+                    array_push(obj->old_texture_ids, model->iqm->textures[i]);
                     model->iqm->textures[i] = (*array_back(obj->textures)).id;
                     if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture) {
-                        array_push(old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
+                        array_push(obj->old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
                         *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = (*array_back(obj->textures));
                     }
                 }
@@ -557,32 +565,80 @@ void scene_render(int flags) {
 
             if ( flags&SCENE_UPDATE_SH_COEF ) {
                 shader_bind(model->program);
-                shader_vec3v("u_coefficients_sh", 9, last_scene->skybox.cubemap.sh);
+                skybox_sh_shader(&last_scene->skybox);
             }
-     
+
             model_skybox(model, last_scene->skybox, 0);
 
+            if (!obj->disable_frustum_check)
+                model_set_frustum(model, frustum_state);
+            else
+                model_clear_frustum(model);
+
             if (anim) {
                 float delta = window_delta() * obj->anim_speed;
                 model->curframe = model_animate_clip(*model, model->curframe + delta, anim->from, anim->to, anim->flags & ANIM_LOOP );
             }
 
-
             model->billboard = obj->billboard;
-            model->rs[RENDER_PASS_OPAQUE].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
-            model->rs[RENDER_PASS_OPAQUE].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
-            model_render(*model, cam->proj, cam->view, obj->transform, model->program);
+            for (int p = 0; p < RENDER_PASS_OVERRIDES_BEGIN; ++p) {
+                model->rs[p].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
+                model->rs[p].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
+            }
+        }
+        
+        /* Collect all transparency enabled models and sort them by distance */
+        static array(object_t*) transparent_objects = 0;
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
 
+            if (obj->skip_draw) continue;
+
+            if (model_has_transparency(*model)) {
+                obj->distance = len3sq(sub3(cam->position, transform344(model->pivot, add3(obj->pos, model->meshcenters[0]))));
+                array_push(transparent_objects, obj);
+            }
+        }
+
+        array_sort(transparent_objects, scene_obj_distance_compare);
+
+        /* Opaque pass */
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_OPAQUE);
+        }
+
+        /* Transparency pass */
+        for (unsigned j = 0; j < array_count(transparent_objects); ++j) {
+            object_t *obj = transparent_objects[j];
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_TRANSPARENT);
+        }
+
+        array_resize(transparent_objects, 0);
+
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    model->iqm->textures[i] = old_texture_ids[i];
-                    if (i < array_count(old_textures)) {
+                    model->iqm->textures[i] = obj->old_texture_ids[i];
+                    if (i < array_count(obj->old_textures)) {
                         if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture)
-                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = old_textures[i];
+                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = obj->old_textures[i];
                     }
                 }
-                array_resize(old_texture_ids, 0);
-                array_resize(old_textures, 0);
+                array_resize(obj->old_texture_ids, 0);
+                array_resize(obj->old_textures, 0);
             }
         }
         glBindVertexArray(0);
diff --git a/engine/split/v4k_scene.h b/engine/split/v4k_scene.h
index b1bee26..f95a8e0 100644
--- a/engine/split/v4k_scene.h
+++ b/engine/split/v4k_scene.h
@@ -48,6 +48,13 @@ typedef struct object_t {
     float anim_speed;
     aabb bounds;
     unsigned billboard; // [0..7] x(4),y(2),z(1) masks
+    bool disable_frustum_check;
+
+    // internal states
+    array(handle) old_texture_ids;
+    array(texture_t) old_textures;
+    float distance;
+    bool skip_draw;
     bool light_cached; //< used by scene to update light data
 } object_t;
 
diff --git a/engine/v4k.c b/engine/v4k.c
index 5a45bd6..28215fd 100644
--- a/engine/v4k.c
+++ b/engine/v4k.c
@@ -20403,12 +20403,19 @@ bool model_load_meshes(iqm_t *q, const struct iqmheader *hdr, model_t *m) {
     q->textures = CALLOC(hdr->num_meshes * 8, sizeof(GLuint));
     q->colormaps = CALLOC(hdr->num_meshes * 8, sizeof(vec4));
     m->meshcenters = CALLOC(hdr->num_meshes, sizeof(vec3));
+    m->meshbounds = CALLOC(hdr->num_meshes, sizeof(aabb));
+    m->meshradii = CALLOC(hdr->num_meshes, sizeof(float));
 
     for(int i = 0; i < (int)hdr->num_meshes; i++) {
         int invalid = texture_checker().id;
         q->textures[i] = invalid;
+        struct iqmmesh *mesh = &q->meshes[i];
+#if 1
         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 < )
+#endif
     }
 
     const char *str = hdr->ofs_text ? (char *)&q->buf[hdr->ofs_text] : "";
@@ -21035,6 +21042,46 @@ int drawcall_compare(const void *a, const void *b) {
     return da->order < db->order ? 1 : da->order > db->order ? -1 : 0;
 }
 
+bool model_has_transparency_mesh(model_t m, int mesh) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    if (m.flags & MODEL_TRANSPARENT) {
+        return true;
+    }
+    if (m.materials[mesh].layer[0].map.color.a < 1 || (m.materials[mesh].layer[0].map.texture && m.materials[mesh].layer[0].map.texture->transparent)) {
+        return true;
+    }
+    if (m.shading == SHADING_PBR && (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[mesh].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+        return true;
+    }
+
+    return false;
+}
+
+bool model_has_transparency(model_t m) {
+    if(!m.iqm) return false;
+    iqm_t *q = m.iqm;
+
+    for (int i = 0; i < q->nummeshes; i++) {
+        if (model_has_transparency_mesh(m, i)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+
+void model_set_frustum(model_t *m, frustum f) {
+    m->frustum_enabled = 1;
+    m->frustum_state = f;
+}
+
+void model_clear_frustum(model_t *m) {
+    m->frustum_enabled = 0;
+}
+
 static
 void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_mat) {
     if(!m.iqm) return;
@@ -21056,13 +21103,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
         required_rs[i] = rs_idx;
 
         if (required_rs[i] < RENDER_PASS_OVERRIDES_BEGIN) {
-            if (m.flags & MODEL_TRANSPARENT) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.materials[i].layer[0].map.color.a < 1 || (m.materials[i].layer[0].map.texture && m.materials[i].layer[0].map.texture->transparent)) {
-                required_rs[i] = RENDER_PASS_TRANSPARENT;
-            }
-            if (m.shading == SHADING_PBR && (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.color.a < 1 || (m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture && m.materials[i].layer[MATERIAL_CHANNEL_ALBEDO].map.texture->transparent))){
+            if (model_has_transparency_mesh(m, i)) {
                 required_rs[i] = RENDER_PASS_TRANSPARENT;
             }
         }
@@ -21102,7 +21143,7 @@ void model_draw_call(model_t m, int shader, int pass, vec3 cam_pos, mat44 model_
                     // calculate distance from camera
                     // @todo: improve me, uses first mesh triangle
                     {
-                        call.distance = len3(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
+                        call.distance = len3sq(sub3(cam_pos, transform344(model_mat, m.meshcenters[i])));
                     }
 
                     if (m.shading == SHADING_PBR)
@@ -21531,6 +21572,8 @@ void model_destroy(model_t m) {
     }
     array_free(m.texture_names);
     FREE(m.meshcenters);
+    FREE(m.meshbounds);
+    FREE(m.meshradii);
 
     iqm_t *q = m.iqm;
 //    if(m.mesh) mesh_destroy(m.mesh);
@@ -23179,8 +23222,16 @@ light_t* scene_index_light(unsigned light_index) {
     return &last_scene->lights[light_index];
 }
 
+static
+int scene_obj_distance_compare(const void *a, const void *b) {
+    const object_t *da = a, *db = b;
+    return da->distance < db->distance ? 1 : da->distance > db->distance ? -1 : 0;
+}
+
 void scene_render(int flags) {
     camera_t *cam = camera_get_active();
+    mat44 projview; multiply44x2(projview, cam->proj, cam->view);
+    frustum frustum_state = frustum_build(projview);
 
     if(flags & SCENE_BACKGROUND) {
         if(last_scene->skybox.program) {
@@ -23206,18 +23257,18 @@ void scene_render(int flags) {
             model_t *model = &obj->model;
             anim_t *anim = &obj->anim;
             mat44 *views = (mat44*)(&cam->view);
+            
+            obj->skip_draw = !obj->disable_frustum_check && !frustum_test_aabb(frustum_state, model_aabb(*model, obj->transform));
 
-            // @todo: avoid heap allocs here?
-            static array(handle) old_texture_ids = 0;
-            static array(texture_t) old_textures = 0;
+            if (obj->skip_draw) continue;
 
             int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    array_push(old_texture_ids, model->iqm->textures[i]);
+                    array_push(obj->old_texture_ids, model->iqm->textures[i]);
                     model->iqm->textures[i] = (*array_back(obj->textures)).id;
                     if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture) {
-                        array_push(old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
+                        array_push(obj->old_textures, *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture);
                         *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = (*array_back(obj->textures));
                     }
                 }
@@ -23231,32 +23282,80 @@ void scene_render(int flags) {
 
             if ( flags&SCENE_UPDATE_SH_COEF ) {
                 shader_bind(model->program);
-                shader_vec3v("u_coefficients_sh", 9, last_scene->skybox.cubemap.sh);
+                skybox_sh_shader(&last_scene->skybox);
             }
-     
+
             model_skybox(model, last_scene->skybox, 0);
 
+            if (!obj->disable_frustum_check)
+                model_set_frustum(model, frustum_state);
+            else
+                model_clear_frustum(model);
+
             if (anim) {
                 float delta = window_delta() * obj->anim_speed;
                 model->curframe = model_animate_clip(*model, model->curframe + delta, anim->from, anim->to, anim->flags & ANIM_LOOP );
             }
 
-
             model->billboard = obj->billboard;
-            model->rs[RENDER_PASS_OPAQUE].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
-            model->rs[RENDER_PASS_OPAQUE].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
-            model_render(*model, cam->proj, cam->view, obj->transform, model->program);
+            for (int p = 0; p < RENDER_PASS_OVERRIDES_BEGIN; ++p) {
+                model->rs[p].cull_face_enabled = flags&SCENE_CULLFACE ? 1 : 0;
+                model->rs[p].polygon_mode_draw = flags&SCENE_WIREFRAME ? GL_LINE : GL_FILL;
+            }
+        }
+        
+        /* Collect all transparency enabled models and sort them by distance */
+        static array(object_t*) transparent_objects = 0;
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
 
+            if (obj->skip_draw) continue;
+
+            if (model_has_transparency(*model)) {
+                obj->distance = len3sq(sub3(cam->position, transform344(model->pivot, add3(obj->pos, model->meshcenters[0]))));
+                array_push(transparent_objects, obj);
+            }
+        }
+
+        array_sort(transparent_objects, scene_obj_distance_compare);
+
+        /* Opaque pass */
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_OPAQUE);
+        }
+
+        /* Transparency pass */
+        for (unsigned j = 0; j < array_count(transparent_objects); ++j) {
+            object_t *obj = transparent_objects[j];
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            model_render_pass(*model, cam->proj, cam->view, obj->transform, model->program, RENDER_PASS_TRANSPARENT);
+        }
+
+        array_resize(transparent_objects, 0);
+
+        for(unsigned j = 0, obj_count = scene_count(); j < obj_count; ++j ) {
+            object_t *obj = scene_index(j);
+            model_t *model = &obj->model;
+            if (obj->skip_draw) continue;
+
+            int do_retexturing = model->iqm && model->shading != SHADING_PBR && array_count(obj->textures) > 0;
             if( do_retexturing ) {
                 for(int i = 0; i < model->iqm->nummeshes; ++i) {
-                    model->iqm->textures[i] = old_texture_ids[i];
-                    if (i < array_count(old_textures)) {
+                    model->iqm->textures[i] = obj->old_texture_ids[i];
+                    if (i < array_count(obj->old_textures)) {
                         if (model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture)
-                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = old_textures[i];
+                            *model->materials[i].layer[MATERIAL_CHANNEL_DIFFUSE].map.texture = obj->old_textures[i];
                     }
                 }
-                array_resize(old_texture_ids, 0);
-                array_resize(old_textures, 0);
+                array_resize(obj->old_texture_ids, 0);
+                array_resize(obj->old_textures, 0);
             }
         }
         glBindVertexArray(0);
diff --git a/engine/v4k.h b/engine/v4k.h
index 2146995..1f761af 100644
--- a/engine/v4k.h
+++ b/engine/v4k.h
@@ -3712,6 +3712,8 @@ typedef struct model_t {
     int num_verts;
     void *tris;
     vec3 *meshcenters;
+    aabb *meshbounds;
+    float *meshradii;
     int num_tris;
     handle vao, ibo, vbo, vao_instanced;
 
@@ -3729,6 +3731,9 @@ typedef struct model_t {
 
     int stored_flags;
     renderstate_t rs[NUM_RENDER_PASSES];
+
+    bool frustum_enabled;
+    frustum frustum_state;
 } model_t;
 
 enum BILLBOARD_MODE {
@@ -3755,6 +3760,10 @@ API void     model_render_instanced(model_t, mat44 proj, mat44 view, mat44 *mode
 API void     model_render_instanced_pass(model_t m, mat44 proj, mat44 view, mat44* models, int shader, unsigned count, int pass);
 API void     model_render_pass(model_t m, mat44 proj, mat44 view, mat44 model, int shader, int pass);
 API void     model_set_texture(model_t*, texture_t t);
+API bool     model_has_transparency_mesh(model_t m, int mesh);
+API bool     model_has_transparency(model_t m);
+API void     model_set_frustum(model_t *m, frustum f);
+API void     model_clear_frustum(model_t *m);
 API bool     model_get_bone_pose(model_t m, unsigned joint, mat34 *out);
 API void     model_destroy(model_t);
 
@@ -3951,6 +3960,13 @@ typedef struct object_t {
     float anim_speed;
     aabb bounds;
     unsigned billboard; // [0..7] x(4),y(2),z(1) masks
+    bool disable_frustum_check;
+
+    // internal states
+    array(handle) old_texture_ids;
+    array(texture_t) old_textures;
+    float distance;
+    bool skip_draw;
     bool light_cached; //< used by scene to update light data
 } object_t;