GR9 Trim Edges Further Information...

Working out a Modelling Strategy

When analysing a design and trying to work out a modelling strategy, try to imagine simpler shapes that can be combined. It sometimes helps to imagine how you might make the design in a workshop from foam or wood.

Some designs can easily be understood as 'constructed shapes', and these are where you will use this approach more often. For other products, like a vehicle exterior, this doesn't really apply, as the surfaces are more like a 'patchwork quilt'.

Modelling strategy for constructed forms

Breaking the Rule

It's usually not possible to complete a whole design without needing to build from a trimmed edge at some point. The next section describes some techniques that can reduce the occurrence of extra spans.

Using the Rebuild Options

When overbuilding isn't a practical option, some tools offer a rebuild option that will improve the quality of the surface derived from the trimmed edge:

Use REBUILD in Rail and Square to improve trimmed edges

Using the Explicit Control

Another option is to use the Explicit Control option to override the automatic parameterisation of the Square or Rail tool. However, often the continuity won't be matched, so you need to use with care.

Use EXPLICIT CONTROL in Rail and Square to improve trimmed edges

Rebuilding the edge with an accurate curve.

This is an advanced technique, and limited because you can only achieve G0 positional continuity to a curve. (Higher continuity has to be achieved by manually sculpting CVs).

For Class A modelling, re-create trimmed edges to improve the parameterisation

Tools that achieve this: