Deciding What to Remove

It's important to decide carefully about where to remove polygons from the geometry. Remove the wrong ones, and the shape of our character will change dramatically. It could also result in bad deformation in the game.

The first two sorts of polygons you should consider for removal are unnecessary polygons and polygons that form shallow angles.

Your model is currently made up of hundreds of polygons, and almost all of them are needed. You may think that a polygon's actual presence means it is necessary to a model, but this is not the case.

So how do you determine which polygons will be unused? An unnecessary polygon is one that does not add to the shape of the mesh, nor does it aid in its deformation.

Look at the two cubes in Figure 5.1. They look exactly the same; the only way they differ is in construction.

Figure 5.1. Although these cubes look the same, they are constructed differently.

Now look at their wireframes in Figure 5.2. You can see that the one on the right contains more polygons than the one on the left. Since the edges are straight, the cube does not need the extra polygons to create that straight edge. If we removed these polygons, the cube would look exactly the same.

Figure 5.2. In the wireframe, you can see that the cube on the right unnecessarily uses far more polygons than the one on the left.

Removing areas that contain shallow angles is also a good way to reduce the polygon count, although this will slightly affect the way the geometry looks.

Take a look at the cylinders in Figure 5.3. Do you see a difference? The one on the right has a very slight bump in it. This is a shallow angle, and it adds so insignificantly to the shape of the geometry that no one would miss it if it were gone.

Figure 5.3. Two cylinders

We now know what to look forunnecessary polygons and shallow anglesso let's move on and begin optimizing our character model.