3D modeling Terminology and definitions
Vertex
A vertex is a single point in 3D space defined by its coordinates (x, y, z). Vertices are the building blocks of 3D models, serving as the "corners" where edges meet. In photogrammetry, vertices are generated during the process of creating a 3D model from photographs.
Triangle
A triangle is a polygon with three vertices connected by three edges. It is the simplest unit of geometry used to define the surface of a 3D model. Triangles are widely used in 3D modeling and rendering because they are mathematically stable and can accurately represent complex surfaces.
Edge
An edge is a straight line connecting two vertices in a 3D model. Edges define the shape of a model by forming the skeleton or framework of its surface. They are essential in defining the structure and topology of a mesh.
Face
A face is a flat surface enclosed by three or more edges. In most 3D models, faces are triangular (triangles), but they can also be quadrilateral (quads) or have more sides (n-gons). Faces define the visible surfaces of a model and are key to creating the appearance of a solid object.
Polygon
A polygon is a flat, two-dimensional shape made up of straight edges that are connected by vertices. Polygons are the building blocks of 3D models and are used to define the surface of a 3D object. In most cases, 3D modeling software represents objects as a mesh, which is a collection of interconnected polygons.
Retopology
Retopology is the process of restructuring or simplifying the geometry of a 3D model to create a cleaner, more optimized mesh. This is often done after creating a dense, high-resolution model through photogrammetry to make it suitable for animation, real-time rendering, or other applications.
Texture
A texture is a 2D image applied to the surface of a 3D model to give it color, detail, and material properties. Textures can include details such as wood grain, metal sheen, or fabric patterns. In photogrammetry, textures are derived from the images used to create the model and are often baked onto the mesh for realism
Mesh
A mesh is the collection of vertices, edges, and faces that define the shape and surface of a 3D object. In photogrammetry, the mesh is created from the point cloud data generated by the software.
Point Cloud
A point cloud is a dense collection of individual points in 3D space, each representing a sampled position on the surface of an object or environment. It is the intermediate output of photogrammetry before creating a mesh.
Normal Map
A normal map is a texture that adds surface detail to a 3D model without increasing its geometry. It simulates small bumps, wrinkles, or other surface irregularities by manipulating how light interacts with the model.
UV Mapping
UV mapping is the process of unwrapping a 3D model's surface and projecting it onto a 2D plane to prepare it for texture application. The term "UV" refers to the axes of the texture space, analogous to X, Y, and Z in 3D space.
Photorealism
Photorealism refers to the creation of 3D models and textures that appear indistinguishable from real-world objects or environments, achieved through detailed geometry, high-resolution textures, and realistic lighting.
LOD (Level of Detail)
Levels of Detail (LOD) are different versions of a 3D model with varying polygon counts. They are used to optimize performance by displaying lower-detail models at greater distances.
Subdivision
Subdivision is the process of dividing a model’s faces into smaller, finer polygons to increase its smoothness and detail. It is commonly used for high-resolution rendering or sculpting.
Decimation
Decimation is the process of reducing the number of polygons in a 3D model while preserving as much detail as possible. It is often used in photogrammetry to make high-poly models more efficient for use in games or real-time applications.
Projection Mapping
Projection mapping involves applying textures or images onto a 3D model based on the perspective of the camera. In photogrammetry, this technique is used to map photographic textures onto a generated mesh.
Scale Bar
A scale bar is a physical object of known size placed in a scene during photogrammetry to ensure the resulting 3D model is to scale.
High-Poly vs. Low-Poly Models
High-Poly Models: Contain a large number of polygons for high detail and are typically used for cinematic or photorealistic renders.
Low-Poly Models: Use fewer polygons for efficiency and are commonly used in games and real-time applications.
Texturing
The process of applying colors, patterns, or materials to the surface of a 3D model. Texturing often includes multiple layers like diffuse maps, normal maps, and specular maps to achieve a realistic appearance.
Baking
Baking is the process of transferring high-resolution details (like textures or lighting information) from one model or texture to another, often from a high-poly to a low-poly model.
Depth Map
A depth map is a grayscale image that encodes the distance of objects from the camera, often used for creating height-based effects or reconstructing 3D geometry.
Scan Alignment
The process of aligning multiple photographic or 3D scan datasets into a single coherent model in photogrammetry or 3D scanning workflows.
Textured Mesh
A 3D mesh with a texture applied, combining geometry and visual details into a single, fully rendered model.
Digital Twin
A digital twin is a highly accurate 3D model of a real-world object, structure, or environment created using technologies like photogrammetry. It is often used for monitoring, simulation, or virtual interaction.