Terminology

Vertex / Vertices

A vertex is a point situated in  a 3D space. By connecting multiple vertices together you are able to create a polygon. They have no mass, as a result they cannot be rescaled, rotated or translated.

Edge

An edge is line that connects two vertices. Unlike a vertex, edges can translated, scaled and rotated to alter the geometry of a shape or object.

Polygon

A polygon is a 2D shape bounded by 3 or more vertices / edges. Polygon modelling is the most popular form of modelling for games.

More polygons in a model allows for greater detail and smoother renders, however it can also mean longer render times.

Triangle

A triangle is the simplest form of polygon,  a single three sided shape, consisting of three vertices / edges. Most 3D engines will require the model to be triangulated on import.

Quad

A quad is a single four sided polygon consisting of four vertices / edges.  In modelling, quads are considered the best form a polygon. This often ensures your model has clean topology, meaning it will deform correctly if animated.

Ngon

An ngon is a single five or more sided shape, consisting of greater than or equal to five vertices / edges. When modelling, the use of ngons should be avoided as issues can occur under rendering including lighting, when texturing and under deformation if animating.

Normal

A surface normal is an invisible vector which your  3D software uses to determine the direction that light will reflect off geometry.  These can be altered to control how light will react on various materials.

Topology

Topology is the way in which vertices, edges and polygons are connected together and flow around a 3D model.

NURB (Non Uniform Rational B-Spline)

NURB surfaces can be simply summed up as a curved line in the 3D modelling software to give smooth edges to a model. Most commonly used on very smooth objects as they require less points than in polygon modelling. A NURBS surface always has four sides which are defined and manipulated through control points.

Bump Map

Bump maps are a 2D copy of your base texture set in grey-scale, used to apply shading to your texture, giving an increased 3D appearance. The brighter the grey, working its way to white, details appear further away from the surface. To contrast that, the darker the grey and closer to black, the further back they appear in the surface. Note that the underlying object geometry is NOT modified when using a bump map, it is more of an illusion.

Normal Map

As in bump maps, normal maps do NOT modify the underlying object geometry.  Normal maps are very similar to bump maps, however instead they use full RGB colour information.  This RGB information tells whatever 3D software you are using the exact direction of the surface is oriented in and how it should be shaded for each and every polygon, as a result,  it provides greater detail than a bump map and is often regarded as the newer / better bump map.

Specularity

Secularity represents to amount of reflectivity a surface has under light.

Objects that would have high specularity are  those that are smooth, glossy or wet.  An example of increased specularity  is a person’s forehead, which will reflect more light and look more shiny due to the amount of oil that can be produced on the forehead.

Objects that would have a low specularity, as they have little ability to reflect light, are those with higher roughness or  matte.

 

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