time to put all this polygon theory to work. In this tutorial,
we'll use Polygon Extrusion to create a nerve cell, called
a ganglia (see Figure 7.23).
7.23 Completed, rendered ganglia.
Start with an Icosahedron.
wavy curve in the Front view, starting at the origin
and heading up in positive Y. Use a B-spline for easy
a primitive icosahedron and leave it at the global center
where it came into existence. (see Figure 7.24).
7.24 The icosahedron and the extrusion path.
Switch to POL
(polygon mode) and select four of the faces with the G supra
key, making sure that you choose non-contiguous (not touching)
faces (see Figure 7.25).
7.25 The icosahedron with four faces selected,
showing the centers.
polygons are selected, each one gets a local center
with the Y axis oriented along the normal of the polygon.
We'll use this local center as a local coordinate system
to extrude each polygon in a different direction.
Extrude Some Arms.
icosahedron selected, bring up the Extrusion dialog
box, and see that the On Curve option is the only option
available. Click Ok and then pick the extrusion path
you drew to complete the command. Arms should sprout
from the selected faces of the icosahedron (see Figure
7.26 The icosahedron with straight extruded
Set the Transform Options.
last command by holding the U Supra key and clicking
anywhere with the left mouse button, until the arms
go away. Now invoke the Surface->Extrusion dialog
again. This time turn on Curve Placement and click the
Transform button to show the transformation options
(see Figure 7.27).
7.27 The Extrusion Transformations dialog,
set for the ganglia.
Scale in X, Y, and Z to 0.8, which makes each successive
polygon 10 percent smaller than the last.
Rotation in Y to 15 degrees, which makes the arms twist
around the direction of the normal as they move out.
dialog, and execute the command to create the armed
ganglia (see Figure 7.28).
7.28 The ganglia with spiral arms.
As you can see,
extruding polygons can yield some interesting results. Extruding
polygons along a path is usefull for making fingers on low-poly
hands, and also for other path extrusion effects like tree
branches and roads. As an extra bonus, being able to transform
a polygon at each stage of the extrusion adds in functionality
like that found in the repetitive duplication tools. Use your
imagination and explore!