Appropriate shading sometimes makes it easier to detect mesh
errors like those shown in Figure 1-13. There are a few unneces-
sary vertices near the left eye that cause a modeling imperfection.
Adding a specular value to the shader makes it easier to detect the
problem and fix it.
Normals
According to the 3ds Max user reference, a normal is a unit vector
that defines which way a face or vertex is pointing. The direction in
which the normal points represents the front of the outer surface of
the face or vertex, which is the side of the surface that is normally
displayed and rendered. This means that when you are not using a
“force two-sided” option and the normal is flipped to the other side,
you will not see the surface. Game programmers use normal manip-
ulations for hardware acceleration and pixel shader effects, but for
modeling purposes what really matters is that the normals show us
the visible surface. It’s where we’ll be working. An extruded face or
edge follows the polygon’s normal.
9
Chapter 1 – Polygonal System Basics
Figure 1-13
Figure 1-14: Left, normals. Right, extruded polygons.
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