Manual Object Culling Reference
Manual object culling is the performance optimization system in Unturned™ that reduces the number of rendered objects by overriding the distance at which specific objects are drawn. By default, the game draws every object at a distance appropriate for its placement context; a chair model placed outdoors is visible from far away because it might function as cover, but the same chair inside a building only needs to be visible while the player is near the building. Culling volumes allow map authors to define zones inside which the contained objects use a shorter render distance, providing a significant performance improvement with minimal visual cost to the player.
57 Studios™ has documented and validated the full manual culling volume configuration surface. This reference covers editing culling volumes in the editor, excluding specific objects from culling, the volumes-owned-by-objects system that has been hiding objects since 2014, the legacy LOD fields for automatic culling volume creation, and the performance testing methodology for evaluating culling volume effectiveness.
Documentation source: This article references the official Smartly Dressed Games modding documentation for the Manual Object Culling chapter and related sections on performance optimization. Community-validated notes from 57 Studios cohort mapping projects are marked where official documentation is silent on a detail.
Who this article is for
This reference is written for Unturned™ map developers who have already built a complete map and are optimizing its rendering performance. If you are new to map creation, start with Custom Map Creation: Project Setup before returning here. Manual object culling is an optimization layer that should be applied after the map layout and object placement are finalized.
What you will learn
- How manual culling volumes work and how they reduce draw calls
- How to create and edit culling volumes in the level editor
- How to exclude specific objects from culling volume management
- How the volumes-owned-by-objects system works and how it affects modded objects
- How to configure the legacy LOD fields for automatic culling volume creation
- How to test culling volume performance with the
-DisableCullingVolumeslaunch option
How manual culling volumes work
Drawing fewer objects is almost always better for performance. The game determines the render distance for each object based on its size, material, and placement context. A large object that might function as gameplay cover (a shipping container) is drawn from far away so the player can see it approaching. A small object that is purely decorative (a chair inside a building) is drawn from a shorter distance because the player only sees it when inside or near the building.
Manual culling volumes allow the map author to override these default distances. A culling volume is a defined zone in 3D space. Every object inside the zone uses a reduced render distance that the volume defines. Objects that are not inside any culling volume use their default render distances.
As shown in the flowchart above, the culling volume system operates during level loading. Objects inside volumes are identified at load time; if an object moves between volumes at runtime (which is uncommon for static map objects), the culling status is not re-evaluated. This is a design choice that prioritizes performance overhead over dynamic accuracy.
The performance trade-off
The official documentation acknowledges the downside of culling volumes. When zooming in on most buildings, it is readily apparent that the interior furniture is missing because it has been culled. The developer who implemented the system experimented with workarounds such as enabling objects near the center of the player's view while zoomed, but concluded that the workaround did not feel any better. The official position is that the performance trade-off is worth it.
Large objects like shipping containers that have higher gameplay importance as cover are excluded from culling volumes by default. Most buildings have their culling volumes inset from the edges slightly so that objects visible through windows are not culled, reducing the visual pop-in effect.
Editing culling volumes
Culling volumes are created and edited in the level editor. The editor provides a checkbox to preview which objects are affected by culling volumes and a refresh button to update the culling association after editing.
Preview Culling checkbox
The level editor has a "Preview Culling" checkbox in the view options. When enabled, all objects inside culling volumes are hidden. This is useful for finding objects that are not included in a culling volume when they should be. During the development of the culling system, the developer realized that the volumes in the vanilla cargo ships did not extend low enough to catch some of the furniture in the crew quarters; the preview mode made this discovery possible.
Refresh Objects button
Objects inside volumes are found when the level is loaded. While working in the editor, the map author can click the "Refresh Objects" button to force the editor to re-find all objects and volumes on the map. This is necessary after moving, resizing, or creating new culling volumes.
Performance cost of volumes
Updating the culling volumes themselves costs some performance. A large number of small volumes may actually make performance worse because the per-volume overhead outweighs the draw call savings from the objects inside the volumes. The official documentation recommends comparing performance with and without culling volumes in dense areas to verify that the volumes are providing a net benefit.
Culling volume size and placement guidance
The 57 Studios cohort recommendation for culling volume placement follows these principles. A single culling volume should cover an entire building interior rather than individual rooms, because the per-volume overhead is significant and multiple small volumes degrade performance. Volumes should be inset from the building's exterior walls by approximately 0.5-1.0 meters so that objects visible through windows are not culled. Volumes should extend from the floor to just above the roof to catch objects on all floors. For multi-story buildings, a single tall volume is preferable to multiple stacked volumes.
| Building type | Recommended volume approach | Rationale |
|---|---|---|
| Single-story house | One box volume covering the interior | Minimal overhead; catches all interior objects |
| Two-story building | One tall box volume | Single volume is cheaper than two stacked volumes |
| Multi-story office building | One volume per 3-4 floors | Prevents the volume from being too tall and catching unintended exterior objects |
| Warehouse with high ceilings | One volume offset to exclude HVAC units | Use negative Z offset (LOD_Size_Z) to exclude rooftop equipment |
| Underground bunker | One volume matching the interior space | Underground objects are naturally hidden but culling still reduces draw calls |
| Open courtyard with low walls | No culling volume | Culling would be visually distracting; objects should be visible at full distance |
Excluding specific objects from culling
Some assets should never be managed by culling volumes. If a decorative object is large enough to serve as gameplay cover, it should remain visible from far away even if it is inside a culling volume zone. The game provides a per-asset exclusion mechanism.
To exclude an asset from culling volume management, add this line to the object's .dat file:
Exclude_From_Culling_Volumes trueFor example, the aerospace facility on the Germany map is excluded from culling volumes. This allows the manually placed culling volumes on the Germany map to hide large objects like shipping containers without accidentally hiding the enormous aerospace facility structure.
Volume ownership and auto-exclusion
Volumes that are owned by objects automatically exclude their owner object from culling. This means that if a culling volume is created from a building prefab's LOD fields, the building itself is not culled even though it is inside the volume. Only the other objects inside the volume's bounds are affected. This auto-exclusion prevents buildings from disappearing when the player stands inside or near them.
Volumes owned by objects
Most vanilla buildings come with default culling volumes that are not selectable because they are not saved in the level file. These invisible volumes have been hiding objects since 2014. The manual culling volume system was introduced in part to make these volumes viewable in the editor, because they have caused confusion over the years, especially for modded objects created without knowledge of their existence.
The official documentation notes that this is an area for future improvement and does not necessarily recommend for or against adding these volumes to custom objects. The legacy system uses old and poorly named fields that can be specified in an object's .dat file to automatically create a culling volume.
Legacy LOD fields for automatic culling volume creation
These fields are very old and poorly named, but they remain functional for creating automatic culling volumes on custom objects.
| Field | Type | Values | Purpose |
|---|---|---|---|
LOD | enum | Mesh or Area | Determines how the culling volume bounds are calculated. Mesh uses the bounds of all renderers on the object. Area uses the size of Occlusion Area components. |
LOD_Bias | float | multiplier | Multiplier for the default 64-meter culling distance. A value of 2.0 means the object is visible up to 128 meters. A value of 0.5 means visible up to 32 meters. |
LOD_Center_X | float | offset in meters | Offsets the volume position along the X axis relative to the object transform. |
LOD_Center_Y | float | offset in meters | Offsets the volume position along the Y axis relative to the object transform. |
LOD_Center_Z | float | offset in meters | Offsets the volume position along the Z axis relative to the object transform. |
LOD_Size_X | float | offset in meters | Adjusts the calculated volume size along the X axis in Mesh mode. |
LOD_Size_Y | float | offset in meters | Adjusts the calculated volume size along the Y axis in Mesh mode. |
LOD_Size_Z | float | offset in meters | Adjusts the calculated volume size along the Z axis in Mesh mode. |
LOD mode behavior
The LOD field determines how the automatic culling volume is sized. In Mesh mode, the volume bounds are calculated from the bounds of all MeshRenderer components on the object. The volume encompasses the full extent of the object's visible geometry. In Area mode, the volume uses the size of any Occlusion Area components placed on the object. The Occlusion Area component does not have any special functionality related to occlusion; at the time it was implemented, it was a workaround to allow placement in Unity with an otherwise unused component. The Area mode is primarily useful for objects whose mesh bounds do not accurately represent the space that should be culled.
LOD_Bias and LOD_Size patterns
The LOD_Bias field is a multiplier on the default 64-meter culling distance. Common values depend on the object's role in the map.
| Object type | LOD_Bias | Effective culling distance | Rationale |
|---|---|---|---|
| Small decorative object (vase, plate) | 0.5 | 32 m | Very short; only visible when player is in the same room |
| Furniture (chair, desk, table) | 0.75 | 48 m | Short; visible within the building interior |
| Medium object (bookshelf, cabinet) | 1.0 | 64 m | Default; visible at standard interior range |
| Large object (bed, sofa, counter) | 1.25 | 80 m | Slightly extended; larger objects are viewable from further away |
| Extra-large object (piano, pool table) | 1.5 | 96 m | Extended; these objects are landmarks within the building |
The LOD_Size fields are offsets that adjust the volume size relative to the mesh bounds. Many vanilla buildings with flat rooftops use a negative LOD_Size_Z value to exclude HVAC units placed on the roof from the culling volume. The 57 Studios cohort recommendation is to use negative Z offsets to exclude rooftop objects and positive Z offsets to extend the volume downward to catch basement objects.
Example: automatic culling volume on a custom building
The following .dat snippet creates an automatic culling volume on a custom two-story building. The volume uses Mesh mode, extends from slightly below the ground floor to just below the rooftop, and has a generous culling distance because the building is a medium-sized structure.
LOD Mesh
LOD_Bias 1.0
LOD_Center_X 0
LOD_Center_Y 0
LOD_Center_Z 0
LOD_Size_X 1.5
LOD_Size_Y 1.2
LOD_Size_Z -0.5This configuration creates a culling volume that is 150% of the mesh width (to catch objects in adjacent rooms), 120% of the mesh height (to extend slightly below and above), and reduced by 0.5 meters in the Z offset to exclude any objects placed on the roof.
Testing culling volume performance benefit
The game provides a launch option to disable all culling volumes for performance comparison:
-DisableCullingVolumesWhen this option is active, no culling volumes are applied. Every object in the level renders at its default distance. By comparing the framerate at the same viewpoint with and without this option, the map author can measure the actual performance benefit of the installed culling volumes.
The official documentation notes that dense urban areas like the Seattle map tend to have the most noticeable difference between the culling-on and culling-off states. A map that shows no measurable framerate improvement with culling volumes may have volumes that are too sparse, too small, or incorrectly placed.
Benchmarking methodology
- Identify the three most object-dense viewpoints in the map. These are typically the center of the most populated town, the interior of the largest building, and a rooftop view overlooking the most dense block.
- At each viewpoint, record the framerate with culling volumes active (normal gameplay).
- At each viewpoint, record the framerate with the
-DisableCullingVolumeslaunch option active. - Calculate the average framerate difference across all three viewpoints.
- If the average improvement is less than 5%, review the culling volume placement and adjust.
- If the average improvement exceeds 10%, the culling volumes are providing good value.
| Benchmark result | Assessment | Recommended action |
|---|---|---|
| 0-3% improvement | Culling volumes ineffective | Remove volumes; they add overhead without benefit |
| 3-8% improvement | Marginal | Consider consolidating or resizing volumes |
| 8-15% improvement | Good | Keep current configuration |
| 15%+ improvement | Excellent | Document configuration for reference in future maps |
Diagnostic table for culling volume issues
| Symptom | Most likely cause | Resolution |
|---|---|---|
| Objects inside building disappear | Culling volume too large or not inset from edges | Inset volume 0.5-1.0 m from exterior walls |
| Furniture pop-in when entering building | Culling volume too small | Extend volume vertically to cover all interior objects |
| Performance worse with culling volumes | Too many small volumes creating overhead | Consolidate volumes; use one volume per building |
| Large objects (containers) disappear | Exclude_From_Culling_Volumes not set | Add the exclusion flag to the object's .dat |
| Building itself disappears when player stands inside | Owner auto-exclusion not working | Add volume directly to building prefab via LOD fields |
| Rooftop objects disappear unexpectedly | Volume extends above roofline | Use negative LOD_Size_Z to exclude rooftop objects |
| Preview Culling shows no hidden objects | Volumes not yet refreshed | Click Refresh Objects in the editor |
| Culling toggle has no effect on framerate | Volumes set incorrectly or too sparse | Review volume coverage; add volumes to dense areas |
FAQ
What is the difference between culling volumes and occlusion culling?
Culling volumes are a manual, author-defined system that overrides the render distance for objects inside a zone. Occlusion culling is an automated system that prevents rendering of objects hidden behind other geometry. Culling volumes are set up in the Unturned™ level editor; occlusion culling is set up in Unity's occlusion culling system. Both techniques reduce draw calls but through different mechanisms. Culling volumes are the more immediately accessible system for Unturned™ map authors because no Unity-side setup is required.
Can I use culling volumes on a map that also uses level batching?
Yes. Culling volumes and level batching are complementary optimization techniques. Culling volumes reduce the number of objects considered for rendering, while batching reduces the draw call cost per object that is rendered. The two systems operate independently and their benefits are additive. The 57 Studios cohort recommendation is to apply both optimizations to any map targeting 60 FPS on mid-range hardware.
Do culling volumes affect the player character or NPCs?
No. Culling volumes only affect static level objects. The player character, NPCs, zombies, animals, and vehicles are not affected by culling volume render distance overrides. This is intentional; dynamic entities must be visible at full range for gameplay reasons.
What happens if two culling volumes overlap?
Objects inside overlapping volumes are managed by only one volume. The engine selects one volume to govern each object; the selection behavior is not deterministic and should not be relied upon. The 57 Studios cohort recommendation is to avoid overlapping culling volumes and to use a single volume per distinct zone.
Can I create culling volumes that hide objects at different distances based on the object type?
No. All objects inside a culling volume use the same reduced render distance determined by the volume's configuration. There is no per-object or per-category distance override within a culling volume. If two objects should have different culling distances, they should be placed in separate volumes.
Do culling volumes work in multiplayer?
Yes. Culling volumes are part of the level data and are applied identically on the client side for every player. Each player's client independently culls objects based on their own camera position. The server does not participate in culling decisions; culling is a purely client-side optimization.
How do I know if a specific object has an owner culling volume?
The volumes-owned-by-objects system creates invisible volumes that are not selectable in the editor. The only way to know if an object has an owner volume is to edit the object in Unity and check its prefab configuration, or to add the object to a scene and observe whether it culls surrounding objects at runtime. The 57 Studios cohort recommendation for modded objects is to explicitly add culling volume configuration through the LOD fields rather than relying on the invisible owner volume system.
Can I remove the invisible owner volumes from vanilla buildings?
The invisible owner volumes are part of the vanilla data set and are not selectable or removable in the editor. They have been a part of the game since 2014 and the system does not provide a removal interface. Map authors who are placing custom objects should focus on configuring their own culling volumes rather than attempting to modify the vanilla volumes.
What is the maximum number of culling volumes I should place?
There is no hard cap, but the performance overhead of each volume reduces the benefit of the system. The 57 Studios cohort recommendation is to use no more than 50-100 culling volumes on a standard-sized map. Maps with more than 200 volumes should be reviewed for consolidation opportunities.
Worked example: culling volume setup for a two-story building
This worked example traces the culling volume configuration for a custom two-story building on a modded map. The building has 10 furniture objects on the first floor, 8 furniture objects on the second floor, and 2 rooftop HVAC units.
Step 1: Analyze the building. The first floor contains chairs, tables, and counters. The second floor contains beds, desks, and bookshelves. The rooftop has two HVAC units that are large enough to serve as partial cover during rooftop combat.
Step 2: Create the volume. Place a single box culling volume in the level editor. Set the volume dimensions to match the building's interior footprint, inset by 0.75 meters from all exterior walls. Set the height from 0.5 meters below the ground floor to 1 meter below the roofline.
Step 3: Exclude rooftop objects. The two HVAC units should not be culled because they function as gameplay cover. Add Exclude_From_Culling_Volumes true to each HVAC unit's .dat file.
Step 4: Test with Preview Culling. Enable Preview Culling. Walk through the building. The interior furniture disappears when the player is outside the building. When the player enters the building, the furniture is no longer culled. The HVAC units remain visible from outside because they are excluded.
Step 5: Measure performance. Run the game with and without -DisableCullingVolumes. The building interior viewpoint shows a 15% framerate improvement with culling volumes active.
Step 6: Verify window visibility. Stand outside the building and look through the windows. Objects visible through windows should not be culled because the volume is inset from the walls. If objects seen through windows are missing, increase the inset distance.
Worked example: automatic culling volume for a custom object
This worked example traces the configuration of an automatic culling volume for a custom object (a market stall with interior shelves). The object is placed as a single prefab in the level and should cull its internal detail objects when viewed from outside.
Step 1: Determine the LOD mode. The market stall has a single mesh renderer covering the entire stall. Use LOD Mesh to create a volume based on the renderer bounds.
Step 2: Set the LOD_Bias. The stall is approximately the size of a large furniture item. Set LOD_Bias 1.0 for a default 64-meter culling distance.
Step 3: Adjust volume center and size. The stall's shelving extends to the edges of the mesh bounds. Set LOD_Size_X 0.9, LOD_Size_Y 0.9, and LOD_Size_Z 0.9 to shrink the volume slightly inside the mesh bounds, ensuring that objects placed on top of the stall (such as a decorative crate) are excluded.
The complete .dat fields:
LOD Mesh
LOD_Bias 1.0
LOD_Center_X 0
LOD_Center_Y 0
LOD_Center_Z 0
LOD_Size_X 0.9
LOD_Size_Y 0.9
LOD_Size_Z 0.9With this configuration, the market stall's internal shelves are only visible when the player is within approximately 64 meters. Outside that distance, the stall structure itself remains visible (the mesh renderer is on the object, not culled), but the internal detail is not rendered because the automatic culling volume has suppressed it.
Culling volume interaction with specific object types
Different object types interact with culling volumes in different ways. Understanding these interactions is essential for correct culling volume placement.
| Object type | Cullable? | Notes |
|---|---|---|
| Static furniture (chairs, tables, counters) | Yes | Primary target for culling volumes in building interiors |
| Dynamic objects (doors, windows) | Yes, but not recommended | Dynamic objects change state; culling may prevent the state change from being visible |
| Large gameplay objects (shipping containers, dumpsters) | No (should be excluded) | These objects serve as cover and must be visible from full distance |
| NPC spawn points | No | NPC spawn points are logic objects with no renderer |
| Decorative props (vases, plates, books) | Yes | Ideal culling volume targets; purely decorative |
| Light sources (lamps, lanterns) | Yes, but not recommended | Culling a light source makes the area go dark even if the light's range would normally reach |
| Trees and foliage | No | Plants use a separate rendering system; culling volumes do not affect them |
| Player-built structures | No | Structures are dynamic; their render distance is determined by the buildable system |
Best practices
- Use a single culling volume per building rather than individual volumes per room
- Inset volumes 0.5-1.0 meters from exterior walls to preserve window visibility
- Test with
-DisableCullingVolumesto measure actual performance benefit - Use the Preview Culling checkbox to verify volume coverage
- Click Refresh Objects after editing volumes
- Exclude large gameplay-important objects with
Exclude_From_Culling_Volumes true - Avoid overlapping volumes
- Keep volume count under 100 for standard maps
- Use negative LOD_Size_Z for buildings with rooftop objects
- Document culling volume placement decisions in the map project notes
Appendix A: Manual object culling quick-reference card
| Task | Method | Notes |
|---|---|---|
| Create a culling volume | Level editor culling tool | Place the volume zone around the target area |
| Preview which objects are culled | Preview Culling checkbox | Hidden objects indicate culling coverage |
| Refresh culling associations | Refresh Objects button | Needed after volume edits |
| Exclude an asset from culling | Exclude_From_Culling_Volumes true in .dat | For large/important objects |
| Test culling impact | -DisableCullingVolumes launch option | Compare framerate with and without |
| Auto-create a volume from object | LOD fields in .dat | For custom objects with building interiors |
Appendix B: Worked example: applying culling volumes to a town
This worked example traces the culling volume setup for a small town with 10 buildings, 30 decorative objects, and 5 large gameplay objects.
Step 1: Identify target buildings. The town has 10 buildings. Three are small houses (one volume each), two are two-story buildings (one volume each), one is a warehouse (one volume with rooftop exclusion), and four are decorative sheds (too small for culling; skip).
Step 2: Place culling volumes. Create 6 culling volumes. For the small houses, place a volume inset 0.5 meters from the walls, from ground to roof peak. For the two-story buildings, inset 0.75 meters and extend the volume 2 meters above the roof to cover all floors. For the warehouse, inset 1.0 meter and use a negative Z offset to exclude the rooftop HVAC units.
Step 3: Exclude large objects. Five shipping containers in the town are set as gameplay cover. Add Exclude_From_Culling_Volumes true to each container's .dat file.
Step 4: Preview. Enable Preview Culling. Walk through the town. Verify that interior furniture is hidden (culled) while window-visible objects remain visible. Verify that the shipping containers remain visible from full distance.
Step 5: Measure. Load the map without and with culling. The framerate in the town center improves by approximately 12% with culling volumes active.
Appendix C: Culling volume LOD field reference table
| Field | Type | Default | Purpose |
|---|---|---|---|
LOD | enum | none | Volume calculation mode: Mesh (renderer bounds) or Area (Occlusion Area size) |
LOD_Bias | float | 1.0 | Multiplier for the default 64m culling distance |
LOD_Center_X | float | 0 | X-axis offset of volume center relative to object transform |
LOD_Center_Y | float | 0 | Y-axis offset of volume center relative to object transform |
LOD_Center_Z | float | 0 | Z-axis offset of volume center relative to object transform |
LOD_Size_X | float | 1.0 | X-axis size multiplier in Mesh mode |
LOD_Size_Y | float | 1.0 | Y-axis size multiplier in Mesh mode |
LOD_Size_Z | float | 1.0 | Z-axis size multiplier in Mesh mode |
Appendix D: External references
- Smartly Dressed Games official modding documentation - the authoritative reference for manual object culling and related performance optimization chapters.
- Level Batching Reference - the complementary optimization technique for reducing draw calls.
- Level Config Reference - the previous article; covers Config.json fields that interact with culling behavior.
- Custom Map Creation: Project Setup - the prerequisite map creation pipeline.
Advanced considerations
Combining culling volumes with object LOD groups
Some custom objects use Unity LOD groups to swap mesh detail at different distances. Culling volumes interact with LOD groups in a straightforward way: when an object is inside a culling volume, its render distance is shortened, which means the LOD group transitions occur at shorter distances as well. A high-detail LOD that was intended to be visible from 80 meters might now be visible only from 40 meters because the culling volume cuts off at that distance. The 57 Studios cohort recommendation is to set LOD group distances conservatively for objects that will be inside culling volumes, because the culling volume override is the primary distance control.
Culling volumes for underground and cave environments
Underground environments and cave systems benefit enormously from culling volumes because the overhead of rendering the entire surface map is eliminated by the cave ceiling. A well-placed culling volume covering the entire underground space can reduce draw calls in the surface area to near-zero while the player is underground, improving framerate in the cave environment significantly. The 57 Studios cohort recommendation is to place culling volumes around the entire perimeter of any underground or cave area, not just inside individual rooms.
Performance profiling for culling volume tuning
The -DisableCullingVolumes launch option is the primary profiling tool, but additional insight can be gained by running the game with the Unity profiler attached. When the profiler is active, the per-volume overhead is visible as a recurring entry in the rendering timeline. This allows the map author to identify volumes whose overhead exceeds their benefit. The 57 Studios cohort recommendation is to run the profiler for at least 30 seconds in the map's most dense area, measure the total time spent on culling volume processing, and compare it to the total time saved by reduced draw calls. If the volume processing time exceeds 10% of the draw call time, the volume configuration should be simplified.
Common culling volume mistakes and how to avoid them
The following table documents the most common mistakes map authors make when setting up culling volumes, based on the 57 Studios cohort's experience across multiple mapping projects.
| Mistake | Symptom | Prevention |
|---|---|---|
| Volume too small for building interior | Furniture visible outside but disappears when entering the building | Extend volume to at least 90% of the building's interior dimensions |
| Volume not inset from walls | Window-visible objects disappear | Inset volume by 0.5-1.0 meters from all exterior walls |
| Too many small volumes | Overall performance worse instead of better | Consolidate volumes; use one per building, not one per room |
| Overlapping volumes from adjacent buildings | Objects in overlap zone have inconsistent culling behavior | Use a single volume covering both buildings or adjust volumes to not overlap |
| Failure to exclude large gameplay objects | Cover objects (containers, walls) disappear at distance | Always add Exclude_From_Culling_Volumes true to large gameplay-important objects |
| Volume extends above roofline | HVAC units and rooftop objects disappear unexpectedly | Use negative LOD_Size_Z to exclude rooftop area |
| Skipping the Preview Culling check | Objects that should be culled are not; no performance benefit | Always enable Preview Culling and walk through the map before publishing |
| Placing volumes in a map that uses level batching | Both systems may over-compete for draw call control | Test culling volumes and batching together before publishing |
The most impactful prevention is to always test with Preview Culling enabled before publishing. The preview mode reveals exactly which objects are affected by culling volumes, allowing the map author to catch placement errors before they affect the player experience.
Benchmarking culling volume efficiency
To determine whether the culling volume configuration is providing value, the following benchmarking approach is recommended.
| Metric | Without culling | With culling | Target |
|---|---|---|---|
| Draw calls (town center) | 1,400 | 1,120 | At least 15% reduction |
| Draw calls (largest building interior) | 800 | 480 | At least 30% reduction |
| Framerate (town center) | 52 FPS | 58 FPS | At least 5 FPS improvement |
| Framerate (building interior) | 65 FPS | 72 FPS | At least 5 FPS improvement |
| Volume overhead (all volumes) | 0 ms | 0.2 ms | Under 0.5 ms total |
If the draw call reduction is below the targets listed above, review the culling volume configuration. The most common cause of insufficient reduction is volumes that are too small or volumes that are placed in areas with very few objects to cull.
Glossary of culling terminology
| Term | Definition |
|---|---|
| Culling | The process of preventing an object from being rendered because it is not within the visible range or is hidden behind other geometry |
| Culling volume | A 3D zone within which objects use a reduced render distance |
| Draw call | A CPU-to-GPU rendering command; fewer draw calls means better performance |
| Exclusion | The mechanism by which a specific object is prevented from being affected by culling volumes |
| Inset | The distance by which a culling volume is placed inside the building's exterior walls |
| LOD | Level of detail; in the culling volume context, LOD fields control automatic volume creation |
| Mesh mode | LOD calculation mode that uses renderer bounds to determine culling volume size |
| Area mode | LOD calculation mode that uses Occlusion Area components to determine volume size |
| Overhead | The CPU time spent evaluating culling volumes; must be less than the GPU time saved |
| Owner volume | An invisible culling volume that is built into an object's prefab and auto-excludes its owner |
Authoring checklist
Before publishing a map with culling volumes, confirm the following:
- [ ] Culling volumes cover all building interiors
- [ ] Volumes are inset from exterior walls (0.5-1.0 m)
- [ ] Large gameplay objects are excluded via
Exclude_From_Culling_Volumes - [ ] Preview Culling shows expected hidden objects
- [ ] Performance comparison shows measurable improvement (5%+)
- [ ] No overlapping volumes
- [ ] Volume count is under 100 for standard maps
- [ ] Rooftop objects are not accidentally culled
- [ ] LOD fields are correctly configured for custom objects with automatic volumes
Advanced considerations for specific building types
Different building types require different culling volume strategies. The following guidance addresses the most common building archetypes that map authors encounter.
Open-plan buildings (warehouses, barns, hangars)
Open-plan buildings have large interior spaces with fewer interior walls. The culling volume should cover the entire interior volume but be inset generously (1.0-1.5 meters) from the exterior walls to preserve the visibility of objects near the open entrance. Because these buildings typically have fewer interior objects than multi-room buildings, the performance benefit of culling is smaller, but the visual cost of culling is also smaller because there are fewer objects to disappear.
Multi-story buildings with open stairwells
Buildings with open stairwells that connect multiple floors present a culling volume challenge. A single tall volume covering all floors will cull objects on all floors when the player is outside, but when the player enters the stairwell, objects on adjacent floors may still be culled because the volume treats all floors as a single zone. The 57 Studios cohort recommendation is to use a single volume for the entire building but to ensure that the volume does not extend into the basement or attic unless those areas also contain cullable objects.
Underground structures and bunkers
Underground structures benefit enormously from culling volumes because the engine would otherwise render surface-level objects that are not visible from underground. A culling volume covering the entire underground area can dramatically reduce draw calls while the player is below ground. The volume should extend from the floor of the underground structure to the ground surface above. Objects at the surface that would be visible through the bunker entrance should be excluded from the volume to prevent them from disappearing when the player looks up through the entrance.
Buildings with glass walls or large windows
Buildings with extensive glass walls or floor-to-ceiling windows need special culling volume treatment. The inset distance must be larger (1.0-1.5 meters) to prevent the culling of objects that are visible through the glass. The 57 Studios cohort recommendation is to place the culling volume such that it begins immediately behind the glass plane, so that objects on the other side of the glass are culled but objects inside the building that are visible through the glass remain rendered.
Culling volume automation through object LOD fields
The legacy LOD field system provides a way to automate culling volume creation on custom objects without requiring manual volume placement in the level editor. This is useful for objects that are placed many times across a map (such as a standard building prefab that appears in 20 different locations). Instead of placing 20 culling volumes manually, the author configures the LOD fields once on the prefab, and each instance of the object automatically creates its own culling volume.
When to use automatic volumes
| Scenario | Recommended approach | Rationale |
|---|---|---|
| Standard building prefab placed 20+ times | Automatic LOD fields | Saves substantial manual placement time |
| Unique landmark building placed once | Manual volume | More precise control over volume shape and inset |
| Small decorative object with interior | Automatic LOD fields | The volume is simple; manual placement is overkill |
| Complex building with multiple interior zones | Manual volumes | Automatic volume cannot create multiple zones |
| Object that already has Occlusion Area components | Automatic (Area mode) | Leverages existing Unity setup |
Setting up the Master Bundle for automatic volumes
For automatic volumes to work correctly, the object's .asset or .dat file must be included in a master bundle location that the map loads. The LOD fields are read from the asset file at level load time, and the engine creates the culling volumes during the same process that creates manual volumes. The 57 Studios cohort recommendation is to include the LOD fields in the asset file that already contains the object's Exclude_From_Culling_Volumes and other configuration fields, keeping all object-level configuration in a single place.
Culling volume compatibility with future Unturned updates
The manual culling volume system is a legacy feature that may be superseded by more advanced rendering optimization systems in future versions of the game. Map authors who invest significant effort in culling volume placement should document their volume configuration in a separate project file so that the configuration can be re-applied if the system changes. The 57 Studios cohort recommendation is to keep a simple text file listing each volume's position, size, and inset values.
Document history
| Version | Date | Author | Notes |
|---|---|---|---|
| 1.0 | 2026-07-26 | 57 Studios | Initial publication. Complete manual object culling reference with volume editing, exclusion, LOD fields, performance testing, and FAQ. |
The document history table tracks all revisions to this article. The initial publication established the complete culling volume reference surface based on official SDG documentation and empirical testing across multiple mapping projects.
Object culling and the map loading process
Culling volumes are applied during the level loading phase, not during gameplay. This means that moving a culling volume after the map has loaded has no effect on the culling state of objects inside it. If a map author wants to change the culling configuration after the map is published, they must update the map and publish a new version. Runtime culling volume changes are not supported by the engine.
Testing tip
When testing culling volumes, start with the most dense building interior on the map. If the culling volumes are providing a measurable benefit in this interior, they are likely providing a smaller but still positive benefit in less dense areas. If the dense interior shows no improvement, the volume configuration needs revision before it is worth testing elsewhere.
The 57 Studios documentation team maintains this reference as part of the ongoing effort to document every optimization and configuration surface in the Unturned modding pipeline. Corrections and additions from the modding community are welcomed through the standard documentation contribution workflow.
Cross-references
- Level Config Reference - the previous article in the mapping section.
- Landscape Material Asset Reference - the next article; covers the landscape material asset type.
- Level Batching Reference - the complementary optimization technique for reducing draw calls.
- Custom Map Creation: Project Setup - the prerequisite map creation pipeline.
- Smartly Dressed Games modding documentation - official field reference.
- Unturned on Steam - game page and community hub.