Volumetric capture and Gaussian Splatting glossary

The terms that come up most when talking about volumetric capture and Gaussian Splatting, explained in a sentence or two.

3D Gaussian Splatting (3DGS): A technique that reconstructs a static scene from photographs and represents it with millions of 3D Gaussians drawn in real time.Guide to Gaussian Splatting
4D Gaussian Splatting (4DGS): The dynamic version of Gaussian Splatting: it reconstructs people and scenes in motion from synchronized cameras.Guide to 4D Gaussian Splatting
6DoF: Six degrees of freedom. The viewer can turn their head and also move through the scene, which 360 video does not allow.
360 video: Video recorded from a single point in every direction. The viewer can look around but cannot move.

Camera synchronization: Making every camera in the rig record at exactly the same instant. It is essential for capturing motion.
Capture rig: The structure that holds the cameras around the capture volume. The one in Dymensium's studio has 120 synchronized cameras.The studio

Densification: The stage of fitting a Gaussian Splatting scene in which Gaussians are added where detail is missing and removed where they are not needed.
Digital twin: A digital replica of a real object, space or process. Gaussian Splatting makes it possible to build twins that look photorealistic.

Gaussian: Each of the elements that make up a Gaussian Splatting scene: a semi-transparent ellipsoid with a position, shape, color and opacity.
glTF: Khronos's standard format for exchanging 3D content. The KHR_gaussian_splatting extension lets it store Gaussian Splatting.Gaussian Splatting formats

Mesh: A surface made of polygons, usually triangles, with a texture on top. It is the basis of traditional 3D.
Motion capture (mocap): Recording the movement of a person's skeleton to animate a digital character. It does not record what the person actually looks like.

NeRF: Neural Radiance Fields. A 2020 technique that represents a scene with a neural network. It produces photorealistic images but renders slowly.

Photogrammetry: A technique that reconstructs a textured mesh from photographs of a still object or space.
PLY: The format of the original 3D Gaussian Splatting paper. Uncompressed and lossless; the standard for editing and archiving.Gaussian Splatting formats
Point cloud: A set of colored 3D points. It is usually the starting point of a reconstruction and also a simple way to represent a scene.

Radiance field: A representation of a scene that gives the color seen from every point in every direction. NeRF and Gaussian Splatting are two ways of building one.
Rasterization: A way of drawing in real time by projecting elements onto the screen. Gaussian Splatting rasterizes Gaussians instead of triangles.

SOG: PlayCanvas's compressed format for publishing Gaussian Splatting on the web. It is 15 to 20 times smaller than a PLY.Gaussian Splatting formats
Spherical harmonics: Mathematical functions each Gaussian uses to store a color that changes with the viewing angle. They reproduce highlights and reflections.
Splat: Each element projected onto the screen when drawing. By extension, a whole Gaussian Splatting capture is also called a splat.
SPZ: An open source compressed format created by Niantic. It is about 10 times smaller than a PLY.Gaussian Splatting formats
Structure from motion (SfM): The process that works out where each photo was taken from and produces an initial point cloud. It is the first step of a Gaussian Splatting reconstruction.

Virtual production: Filming in which digital sets are shown in real time, on LED screens for example, while the actors are recorded.
Volumetric capture: Recording a person, an object or a space from many angles to reconstruct it in 3D and view it from any point of view.What is volumetric capture
Volumetric video: Volumetric capture of a subject in motion: a recording that can be watched from any angle.4D volumetric capture

WebGL and WebGPU: Technologies that let the browser use the graphics card. They make it possible to view Gaussian Splatting on a website with nothing to install.

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