Terminology

This document is meant to establish the naming and terminologies of common terms you’ll encountering when capturing and processing photogrammetry models.

3D Terms

• PG: Shorthand for photogrammetry
• 3D Scan / 3D Capture / Photogrammetry Capture: For the sake of simplicity, we can use these terms interchangeably. They all refer to a method used to capture an environment to process into a 3D model.
• Mesh: A set of triangles (polygons) that make up the surface geometry of the 3D model.
• Vertex / Vertices: A point connecting the edges of a triangle.
• Texture: A color layer on the surface of a mesh. In this context, it is made by projecting the colors from the photogrammetry images onto the surface of the mesh.
• Vertex Color: A way of adding color to a mesh by coloring each vertex. Vertex coloring is different than texture coloring because the resolution of the colors depends on how many vertices there are rather than the resolution of a texture.
• Decimation/Simplification/Reduction: Reducing the amount of triangles in a mesh while maintaining the overall shape of the model.

PG Capturing Terms

• Dataset: A set of images captured of a subject or location for PG processing.
• Parallax: A type of capturing movement in which you move laterally with your camera. While looking straight ahead, take a step to your left or right while looking in the same direction to “move with parallax”.
• A Run: A set of consecutive images in a photogrammetry dataset.
• An Orbit: An inside-facing circular run. With the camera facing the subject, the photographer moves around the subject laterally in a circular motion, capturing images along the way to create an “orbit of images”.
• “Branching off”: A way to ensure the images of a new run align with the previously captured images. This is achieved by starting a new run at the same position of an image captured in a previous run.
• Motion Blur: An unsharp image with the pixels streaking in the direction the camera was moved during capture. Motion blur typically happens while capturing handheld images with a slow shutter speed.
• Unsharp Image: An image that is not as sharp as it could be. Unsharp images are caused by bad focus, motion blur, or too much depth of field.

PG Terms

• Alignment (camera alignment / registration): Images successfully aligning with one another in PG software, enabling the algorithm to determine the relative positions of the photos to each other. The success of the alignment depends on if the images share a similar view of the captured subject (overlap) and are sharp enough for the software to detect enough features.