Computer Graphics: Topology

Topology

When referring to computer graphics, 3d models and the like, topology is the wireframe of a given object. The wireframe is comprised of all the vertices (where lines meet to form a point), edges (the lines made up of two connects vertives) and from that information the faces can be made (generally have 2-3 connected edges per face). Now, as I pointed out in a previous blog I said that optimization was immportant for computer graphics. Today, I will go over "proper" topology.

Proper Topology?

Proper topology is the arrangement of the wireframe so that enough detail is present in the model while also keeping the polygon (faces) count to a manageable number (as low as possible while keeping necessary detail). In animation, proper topology goes one step further because it allows the model to deform more naturally when moving. (Bad topology example) (Good topology example)

Of course, there are no guides to proper topology for every single object that can be created but there is often discussion of maintaining edge flows/loops which are ringes of vertices/edges that can circle features of models. Human faces has more documentation for this and typically have the similar edge loops. This doesn't mean edge loops are not applicable to other models. See a few edgeflows in the Purple Page Eater. Even though he lacks a nose and a second eye, I still tried to keep edgeloops around his mouth and eyeball as seen in human facial wireframes.

Controling Topology

As I have been learning, these are some common methods used when dealing with topology in meshes.

1. Edgeflows, as stated previously, these are flows of vertices/edges that can circle areas but can terminate early just forming a line. The purpose of this is to provide more natural deformation. Notice here, that the loops around the eyes follow the muscles under the skin.

2. Poles, or where 3 or 5 edgeflows meet to terminate. These are general places where no animation occurs or where the mesh naturally crinkles as seen in this image.

3. Tri's (when still working with topology). These are basically triangles and often used to terminate edgeflows they tend to be hidden, like behind ears. The purpose of these is to preserve polygon count and often are used instead of adding an extra edgeloop that would create many more quads (square faces). In short, having 1 tri and is better than adding 8 or more quads. But note, tris are still used and seem to be a finalizing process, particularly in games (game model example).

Conclusion

To surmise, having proper topology is a good thing for the computer (less render time!) and animation (as well as some other processes like UV mappning). However, this adds anothing layer for me and others to think about when creating 3D models.

Interested in this topic? Then go here! He does a fairly good job in explaing the subject, I even used some of his images as reference.He also mentions a few workflows.

 

X
Enter your linkblue username.
Enter your linkblue password.
Secure Login

This login is SSL protected

Loading