The mesh of vertices, a cube

is created by 8 vertices, 18 edges and 12 triangles.

PLY File

Is a computer file format know as the polygon file format of the standor triangle format. It was principally desgined to store three-dimensional data from 3D scanners. The data storage foramt supports a relatively simple description of a single object as a list of nominally plat polygons.

OBJ file

Wavefron OBJ file format is a format for defining the 3D geometry for the surface of one or more objects. Object files define the geometry and other properties for objects in Eavefront advanced visualizer. Objec files can also be used to tranfer geoetric data back and forth between the advanced visualizer and other applications.

Sub types of polygon mesh

  • Closed mesh: A mesh whose boundary is zero, or which does not have a boundary
  • Manifold Mesh: Is a polysurface or mesh ofr which every edge is shared by at most two faces is called a manifold.
  • Non manifold geometry; is a mesh taht cannot be unfolded into a flat surface with the one directed normal and cannot exist in the real world.

Mesh data structure

If we only need to perfor some basic operations. Loading and rendering a mesh on screen, we can use very basic mesh data structures such as polygon soup.

  • A polygon soup is a list of vertices together with a lsit of polygons referencing the vertices, such in a ply or obj file. However these formats don tfacilitie meangniful traversal of polygon meshesl and is therefore often not sufficient for many geometry taks

Task that you cannot handle with OBJ and PLY its not possible to represent subdivision surfaces, NURBS or implicit surfaces. PLY support clouds points in a simple manner, OBJ dont support this, particularity when the points lack of connectivity. LAZ or LAS formats support other kind of attributes as color, intensity, or normals. For tasks that requires complex textures mappings, multi-layered materials or advanced shaders to photorealistic rendeting, these files cannot proprielly do this. OBJ and PLY are static mesh formats, they don not natively support animation or skeletal rigging, movement or deformation over the time. FBX, collada or alembic are design to hanfle dynamic, aniamted, content, including rigging and ske;eta; strucutres, along the transformations over time.