3DGS Scene Clipping and Sectioning

The three tools act at different stages: clipping volumes and section planes only change the final rendering, and the data loads as usual; a load volume acts before loading, so excluded areas are never read at all.

Note: clipping volumes and section planes clip the rendered image only by default; collision in the clipped-away areas is still kept. When collision should be removed along with the clipping (so a character does not run into an invisible wall), enable Clip Collision; see Collision - Clip Collision Regions.

Clipping Volumes

A clipping volume can be scaled, moved, and rotated freely, which helps developers clip an LCC scene spatially.

• A single Actor supports up to 65536 clipping volumes, limited to 50 in the free edition; see Editions and Licensing
• Box and sphere shapes are supported, and both can be scaled, moved, and rotated

Note: clipping only affects the final rendering. Clipped-away areas still take part in node traversal, load, and video memory upload as usual. Clipping therefore cannot reduce the load amount or video memory usage; use the methods in the Performance Guide to control those costs.

Steps

1. Place an LCCActor/LCC2Actor and load the scene.
2. Drag LCC Clipping Volume into the scene.

Dragging an LCC Clipping Volume into the scene

3. Move the clipping volume to the target position.
4. Add the Clipping Volume to the ClippingVolumes array in the Details panel of the Actor.

The Inside clipping result of a clipping volume

Demo

Moving a clipping volume and observing the clipping in real time

Properties

Blueprint Methods

LCCComponent → AddClippingVolume
LCCComponent → RemoveClippingVolume

Note: Refresh and SetUpdateComponent are deprecated. Clipping data is read every frame, so changing a property or moving a clipping volume takes effect on the next frame without calling them.

Adding, removing, and refreshing a clipping volume with Blueprint nodes

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Section Planes

A section plane can be scaled, moved, and rotated freely to section the scene along a plane.

• A single Actor supports up to 65536 section planes, limited to 50 in the free edition; see Editions and Licensing
• Sectioning upward or downward is supported, and the count is tracked separately from clipping volumes

Note: sectioning only affects the final rendering. Sectioned-away areas still take part in node traversal, load, and video memory upload as usual. Sectioning therefore cannot reduce the load amount or video memory usage.

Steps

1. Place an LCCActor/LCC2Actor and load the scene.
2. Drag LCC Section Plane into the scene.

Dragging an LCC Section Plane into the scene

3. Move it to the target position.
4. Add the Section Plane to the SectionPlanes array in the Details panel of the Actor.

Demo

Moving a section plane and observing the sectioning in real time

Properties

Blueprint Methods

LCCComponent → AddSectionPlane
LCCComponent → RemoveSectionPlane

Note: Refresh and SetUpdateComponent are deprecated, for the same reason as above.

Adding, removing, and refreshing a section plane with Blueprint nodes

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Load Volumes

A load volume filters the data before it enters memory: node traversal only keeps the nodes it selects, and the data in rejected areas is never read. It is therefore the only one of the three tools in this document that genuinely reduces the load amount and video memory usage, which suits taking a small part out of a large scene.

• Box and sphere shapes are supported, and both can be scaled, moved, and rotated freely
• One load volume can affect multiple LCC Actors in the scene at the same time
• A Pro edition feature; without a license it has no effect and the data loads over its full extent. See Editions and Licensing

Note: filtering works per node, so the border is coarser than a clipping volume's. When a precise border is needed, stack a clipping volume with the same transform on top: the load volume reduces the load amount and the clipping volume trims the edge.

Steps

1. Place an LCCActor/LCC2Actor.
2. Drag LCC Load Volume into the scene.
3. Adjust position, rotation, and scale so the volume frames the range to keep.
4. Add the Load Volume to the LoadVolumes array in the Details panel of the Actor.
5. Load the scene.

Note: filtering happens at load time. After loading has finished, changing the load volume requires reloading before the change is visible.

Properties

The two modes use different border tests:

Both modes are deliberately conservative, which keeps areas from popping in and out while the camera moves and the LOD switches between parent and child nodes.

Blueprint Methods

LCCComponent → AddLoadVolume
LCCComponent → RemoveLoadVolume

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