Class 12: How 3D Computer Graphics Work

For this assignment, we have to explain how 3D graphics work, taking a list of terms associated with 3D graphics, one by one, and defining them as they pertain.  I am going to take these terms in groups of three or four and explain their independent definitions as well as their relations to the other terms.  First, we have 3D Geometry.  3D geometry is something we have learned from the very first time our parents had us place different-shaped puzzle pieces into their corresponding slots in our cribs.  It is one thing to see a circle two-dimensionally, but when we see it as a 3D sphere, THAT is an advance in 3D geometry (See figure 1).  

Figure 1:

The second term(s) we have is "vertex points."  For this definition, I go back to high school geometry when we learned about 90 and 45 degree angles, just to rattle off two different examples.  For this example (Figure 2), I have chosen a 45 degree angle, illustrating that the vertex is the exact point where the X and Y vertices intersect.  Which also brings me to the third term to define: vertices.  Vertices is just the plural of vertex.  So in terms of 3D graphics, a 3D pyramid would have several vertices, as seen in Figure 3.  Fourth, we have the term "vector."  When it comes to 3D graphics, a vector is essentially the 2D figure that, when combined with other 2D graphics, creates a 3D graphic.  For example, each 2D triangle that is a side of a pyramid IS a vector (Figure 4).

Figure 2:

Figure 3:

Figure 4: 

Next, we have the term "polygon."  A polygon is ANY shape or figure that is connected, or made whole, by nothing other than straight lines (See Figure 5).  Which leads to the next term, "polygonal mesh."  Polygonal mesh is a collection of different vertices, vectors, and figures (2D) that, when put together, give the illusion of a 3D object (See Figure 6).  The example in Figure 6 is made out of all triangle vectors.

Figure 5:

Figure 6:

Next, we have the term "normal" as it is related to 3D computer graphics.  Just as we used to learn about tangent lines in geometry, a "normal" is essentially the same thing, but three dimensional (Figure 7).  A normal, if connected to the Y axis, is a perfect 90 degree angle from the tangent at any point on said plane.  

Figure 7:

Finally, we have lighting, shading, and texture mapping.  All three of these terms play in to each other.  For example, The lighting in Figure 4 (pyramid) is coming from the right hand side of the image, and the shading is exemplified by the darker left hand side.  TOGETHER, these two aspects of 3D graphics come together and help with texture mapping.  Below (Figure 8) is an example of a 3D model without texture mapping (1) versus a 3D model with texture mapping(2).

Figure 8: