Occlusion Culling

The occluder is a box shape that culls objects' surfaces, bounds of which aren't visible behind it. This is the simpliest type of occluders that should be used together with box-shaped objects that block off other objects. For example, you can add an occluder the shape of which coincides with the bounds of a building to avoid rendering of objects behind this building.

To create a box-shaped occluder, perform the following:

1. In the Menu Bar, choose Create -> Optimization -> Occluder and add the occluder as a child to the node that should occlude other objects.
2. In the Common section of the Node tab in the Parameters window, set the position of the occluder to the parent one.

   

3. In the World Occluder section of the Node tab, click Edit Size to enable the editing mode for the occluder. Resize the occluder by using the colored rectangles on the occluder box sides so that it coincides with the parent node size.
   Notice

   You can also use the Size parameter to set the size along the axes.

   

4. Specify the Distance between the camera and the occluder, at which the occluder doesn't occlude anything and, therefore, should be disabled to avoid negative impact on the performance.

   

To check how the occluder works, disable the parent node and then try to toggle the occluder on and off:

By default, the front faces of the occluder are used to cull objects. However, if the camera is inside the occluder (e.g. inside the building), occlusion culling won't be performed. To avoid such situation, enable the Back Face parameter in the World Occluder section of the Node tab.

The occluder mesh is based on an arbitrary mesh that culls objects' surfaces, bounds of which aren't visible behind it. The occluder mesh is used together with the geometry that cannot be approximated with a box.

To create a mesh-based occluder, perform the following:

1. Prepare a low-poly mesh to be used for the occluder.
   Notice

   It isn't recommended to use the same detailed mesh that is used for the node that should occlude other objects: the mesh for the occluder should be as simple as possible to avoid performance loss.

   

2. In the Menu Bar, choose Create -> Optimization -> Occluder Mesh and specify the prepared mesh.
   Notice

   You can load a new mesh for the occluder at any time.
3. Add the occluder as a child to the node that should occlude other objects.
4. In the Common section of the Node tab in the Parameters window, set the position of the occluder to the parent one.

   

5. Specify the Distance between the camera and the occluder, at which the occluder doesn't occlude anything and, therefore, should be disabled to avoid negative impact on the performance.

   

The occluder terrain culls objects' surfaces, bounds of which aren't visible behind the terrain geometry. The occluder terrain repeats the shape of the terrain. It is highly effective on scenes containing:

• A terrain with fluctuating heights.
• A lot of objects with complex geometry that can be occluded by the terrain geometry. However, such objects shouldn't be too large in order to be successfully culled by the terrain occluder (since if any part of their surface is seen, it cannot be culled).

It is not recommended to use the occluder terrain in the following cases:

• If the terrain is flat: the occluder will decrease the performance as there would be no surfaces to be culled.
• If the terrain relief is changed in runtime.
• If the terrain is observed from above (e.g., in case of flight simulators).
  Notice

  If the camera can go below in such scenarios, set up the occluder terrain that is enabled/disabled at a certain distance to improve the performance.

To create an occluder terrain, perform the following:

1. In the Menu Bar, choose Create -> Optimization -> Occluder Terrain and place it in the center of the terrain.
2. In the World Occluder Terrain section of the Node tab, set the Size of the occluder so that it coincides with the the terrain size. The whole terrain should be covered with the occluder.

   

3. In the Heights parameter of the World Occluder Terrain section, specify the same height map that was used for the terrain generation, but downscaled for optimization purposes.

   

Check the result: look through the terrain geometry to the occluded objects and try to toggle the occluders rendering on/off.

A sector allows culling all objects outside its volume. Sectors are used to split the world into two areas: inside and outside the sector. They can significantly improve the performance in complex scenes with large indoor and outdoor parts: when you are inside a room, objects outside this room aren't rendered.

To create and set up a sector, perform the following:

1. In the Menu Bar, choose Create -> Optimization -> Sector and add the sector to the world.
2. In the World Sector section of the Node tab, Parameters window, specify the size of the sector, so that it coincides with the room size.

   

3. Move the sector to match the position of the room. You can also add the sector node as a child to the room node and set the sector's position to the parent one.

   

In the result, the interior won't be visible, when the camera is outside the room and vice versa.

A portal allows connecting sectors: it provides an opening through which an interior of one sector is visible from another sector. Portals don't have any positive impact on the performance: they only make the scene more realistic.

To create a portal, perform the following:

1. In the Menu Bar, choose Create -> Optimization -> Portal and place it on a face of a sector. The portal must become green: it means that the interior of the sector will be visible through the portal.

   

2. In the World Portal section of the Node tab, Parameters window, set the Width and the Height of the portal. Also you can adjust the size in the editing mode that is activated by pressing Edit Size.