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Self-intersecting Checks in Sweeping
Potential self-intersecting sweeps can be caused by paths that bring the profile cross-sections to intersecting positions or non-planar profiles. Another method of creating a potential self-intersecting sweep is using a draft that will cause faces from different edges of the profile to intersect each other. Because self-intersecting bodies are not valid in ACIS, sweeping provides some methods to reduce the chances of creating a self-intersecting sweep.
When the path specified is a helix, sweeping automatically checks to see if the profile will intersect itself at successive turns of the helix. If the height of the profile relative to the axis direction is equal to or greater than the pitch of the helix, sweeping prevents the creation of a self-intersecting body. It is recommended that at least SPAresfit clearance between successive turns of the helix be allowed. This will improve the robustness of the resulting body.
The sweep method set_self_int_test() enables a self intersecting test that is carried along the sweep operation. It has three states : do not perform check (0), perform check and error (1), perform check and throw warning (2). The option is set to 1 as default. If you desire to complete the body, regardless of the intersection, the option can be set to 2 or 0. Some performance can be gained by disabling the test, but there is the risk of producing a body that is irregular, faulting down stream, use with a good reasoning.
The option header "careful" performs even more stringent checks for self-intersecting sweeps. These checks also look for combinations of faces created during sweeping that are intersecting. This check is another decrease in performance and is off by default.
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