## Buzz’s Blog: On Web 3.0 and the Semantic Web

Jun 2 2011   6:44PM GMT

# Straight line 3D modeling with polygons, part 4

Profile: Roger King

Curved line vector modeling for 3D graphics.

In five recent postings, (12345), we looked at the simple, powerful mathematical techniques that underly the specification of curved lines in 3D graphics and how they are used to create 3D models.

Straight line vector modeling for 3D graphics.

In the last three postings (678), we turned to straight lines, and how 3D models can be built entirely out of 2D straight lines, using polygons.  We also looked at the minimal information a graphics or animation application must manage in order to unambiguously represent a 3D object created with straight line geometry – and we saw that it isn’t very complicated at all.

We left off with a Moai that we were modeling using polygons and a handful of very simple Autodesk Maya tools.

Using edge loops to add geometric detail.

Consider the image below.  It shows the Moai statue that we began to build in the last posting of this blog.  We have added more edge loops to give us the detail we need for pulling out the features of our Moai from the cylinder with which we began.

We have selected vertices on these edge loops and pulled on them to create the nose and the mouth of our Moai.

Pulling edges to make the facial features.

Consider the image below:

We have continued to mold the facial features out by selecting edges on the object and pulling them out.  This way, we turn the very narrow features we created by pulling on vertices into wider features that begin to resemble a face.

There is a general concept here: manipulating vertices, edges, and faces.

With polygon modeling, we create an object out of a mesh of polygons.  To craft the model, we can select vertices (where edges of polygons meet), edges (the lines that form polygons), and faces (the surfaces of the polygons themselves) and push/pull them to craft out model from a geometric primitive – in this case, a cylinder that has been sliced in half.

More next time.