Extend Surfaces Subpanel

Use the Extend Surfaces subpanel to access several controls that affect how surfaces are identified and generated.

Panel Options

Option Action
min. angle between surfaces Surfaces whose angle relative to one another is less than this value will not be extended toward each other.
max edge to surface angle Edges that you wish to extend must not be too drastically angled relative to the target surfaces. Edges angled greater than this number of degrees relative to their target surfaces will fail to extend.
allow shortening Shorten surfaces rather than extend if they are extended less than the max extension distance beyond another input surface edge.
allow inter-comp extension Extend surfaces toward surfaces that exist in a different component. When disabled, you can only extend surfaces to other surfaces within the same component.
use guide edges Edge extensions without this option are straightforward, with edges extending along their normal. With this option, the extension uses the edges adjacent to each extending edge as an indicator to trim the extended surface and maintain a similar shape for the surface. In addition, when using the extend over edges method instead of the max extension method, a new lines: guide edges to ignore selector allows you to select adjacent edges to omit from consideration as guides.

Figure 1.
You can also automatically exclude some edges from consideration as guides by means of the minimum angle to guide edge field. Edges less than this angle relative to the extended edge will not be used as guides. This limit works for both the extend over edges and max extension methods.

Extended Trapezoidal Surfaces is an example where the use of guide edges are a necessity to avoid undesirable results.

create new surfaces for extension Instead of extending the existing surface, a new surface is created to fill the gap between the original surface and the target of the extension. The original surface is left unchanged. When this checkbox is selected, additional sub-options are enabled.
single surface extension
Create a new surface that is coplanar and identical to the original surface, then perform the extension on that surface instead of the original.
surfaces by edges extension
Create a new connecting surface in the gap between the original and the target.
create in: Choose where to organize component extensions.
original component
Keep the extended surfaces (including any new surfaces created via the create new surfaces for extension option) in the extended surfaces' beginning components.
extended surfaces component
Copy the original surfaces into a new extended surfaces component, and perform all extension operations on those copies within the new component.

Extended Trapezoidal Surfaces

In some cases, extending or shrinking the parallel edges of trapezoidal surfaces without using guide edges can produce unexpected results. This occurs because the extension is performed normally to the edges being moved. In the case of shortened edges this can result in sliver-shaped remainders, because the non-parallel sides do not get shortened, as shown in Figure 2.

Figure 2.

Using the use guide edges option allows the guide edges themselves to be shortened, thus avoiding this issue.

Using the same starting surface, the following results are obtained under these circumstances.

Figure 3. Guide Edges Off, Elongation

Figure 4. Guide Edges On, Elongation

Figure 5. Guide Edges Off, Shortening

Figure 6. Guide Edges On, Shortening