3D Modelling Software

There are many software used for 3D modelling. A few examples are Autodesk Maya, Cinema 4D and Blender. Autodesk Maya is a 3D graphics application, used to create assets in films, television, video games and architecture, originally released in 1998 but bought by Autodesk in 2005. Cinema 4D is a 3D modelling, animation, motion graphic and rendering application. It's used for modelling, animating, lighting, texturing, rendering, and other common features found in 3D modelling applications.Currently, there has been 5 variants, and was originally developed for Amiga computers in the early 1990s. Blender is a free open-source 3D computer graphics software, first made in 1995. It is used for creating animated films, visual effects, art, 3D printed models, interactive 3D models and video games. It includes 3D modelling, texturing, sculpting, rendering and much more.

Geometric Theory
Edges - Shows each line that went into making a shape. Certain shapes, such as curved shapes, have a large amount of edges, because they are made up of a large amount of straight lines.
Vertices - Where two edges meet. There will be two vertices on the end of an edge's straight line. Curves need a large amount of edges to be made, and they also need more vertices to be created. They're given coordinates to calculate their exact location.
Polygons - Turns a 3D skeleton into a shape and makes up the surface/faces of the shape. 3 sided shapes are known as trigons (triangle), 4 sided shapes are known as quadrons (square), 5+ sided shapes are known as n-gons (pentagon).
Face - Used for flat surfaces of 3D shapes, and creates the boundaries of the shapes. The faces make up the overall look of the shape. A 3D solid made from flat surfaces is known as a polyhedron.
Co-ordinate geometry:
 2D co-ordinates - The length and width of an object. Needed to create objects at a specific size, and to pinpoint where objects will be placed.
 3D co-ordinates - The length, width and depth of an object. Has more outcomes than 2D co-ordinates. They are important because they can be used to create 3D models and make them into different objects.

Mesh Construction 
Mesh Construction is creating objects with polygon meshes. The polygons are different forms of elements. The elements are the ones in Geometric Theory.
Box Modelling - A primitive shape (e.g. box, cylinder, sphere) is used in the final model as the basic shape.
Extrusion Modelling - Similar to Box Modelling, but is also a lot different. It starts with a single object, and the object is extruded and can be shaped in any way. It isn't able to create complex objects.

Constraints
Polygon Count - Having a certain amount of polygons in a 3D polygon.When creating a model, you need to keep control of how many polygons it has. The amount of polygons could affect how the game runs. Because everyone has different processors in their computers, the polygon count is also different.
File Size - Available in many sizes. The smallest file size can load up the fastest, whereas the biggest file size can hold more polygons.
Render Time - Using a certain render engine will cause a longer loading time.
LOD - Level of Detail. A concept in 3D modelling used to indicate how much detail needs to be modelled.