Graphics Reference
In-Depth Information
This serves to illustrate an important point about SubD modeling: To define an edge with geometry, edges
must be added to define the incoming and outgoing curve shape. When edges are created close to a corner,
the result is a sharp crease. The farther these edges lie from the corner, the more rounded the corner will
become. There are several methods for adding these
control
edges.
The Loop Slice tool is excellent for adding edges around strips of adjacent polygons or directly perpen-
dicular edges. To use this tool, select two adjacent polygons (or perpendicular edges), activate the tool loc-
ated in the Mesh Edit tab, and click in the viewport. The tool updates live so you can increase the number
of edges and their positions while viewing the updates to the model in real time. Setting the tool mode to
Symmetry and using two edges will enable you to add creases to the two sides of the polygon loop at once.
When dealing with individual edges that require sharpening that is the same incoming and outgoing, the
Edge Extrude and Edge Bevel tools (accessed by clicking the Extrude or Bevel buttons in the Edge tab of
the modo Tools toolbar) are particularly useful. Despite their similarities, these two tools work in very dif-
ferent ways. The Edge Bevel tool creates a chamfered edge around the selected edge or edges. This can be
used in polygonal modeling to round corners, but in SubD modeling it sharpens them. This tool should be
used carefully, however, because the resulting
polygonal structure
is actually rounded and not a sharp, thus
making it more difficult to achieve a sharp crease. The Edge Extrude tool, however, creates new edges that
slide along the polygonal surface and away from the selected edge(s) because no rounding is occurring. This
tool is preferable for creating very sharp creases in geometry.
Figure 5-3
shows a staircase with extruded edges that gradually move away from the corners. The Ex-
trude setting of the Edge Extrude tool moves the original edge away from the surface when positive values
are used, or indents the edge when negative values are entered. This can be useful for creating sweeping
additions to the model surface. The effect of the Edge Extrude tool along with examples of outward and
inward extrusion are shown in
Figure 5-4
.
Figure 5-3:
A subdivided staircase and its unsubdivided counterpart are shown with sharpening edges
moving away from the corners.
