Shelling and Offsetting
List of: Discussion Topic
Subjects: Tolerant Modeling
Contents: Kernel

In many cases, creating tolerant near tangent edges in local operations makes shelling and offsetting faster and more reliable. The offset is faster since surfaces adjacent to the near tangent edge do not have to be extended or intersected. The offset is more reliable since near-tangent surface intersections are typically hard and are prone to fail.

The following examples show some of the shelling applications for tolerant modeling.

This model cannot be shelled unless the option lop_near_tangent is TRUE, since the adjacent surfaces on the near-tangent edges (shown in blue) do not intersect.

Figure 6-4. Swept model cannot shell without tolerant modeling

Figure 6-5. Shelled with tolerant modeling

Shell characteristics:

box size is: 12.6 x 16 x 8

thickness is: 2.0

tolerance is: 4.3e-12

res_near_tangent is: 0.0175 (about 1 degree)

In the following example, the difficult intersection between the variable radius blend surfaces causes this shell to be significantly slower without tolerant modeling.

Figure 6-6. Variable radius blend

Figure 6-7. Shelling with tolerant modeling is faster

Shell characteristics:

15.89 sec with TM vs. 105.87 sec without TM

box size is: 11.6 x 11.6 x 2.1

thickness is: -0.25

tolerance is: 0.022

res_near_tangent is: 0.08 (about 4.6 degrees)