Options for Tolerant Modeling
List of: Discussion Topic
Subjects: Tolerant Modeling
Contents: Kernel

These options affect and control tolerant modeling for different operations in ACIS. Review the reference templates before you use them.

Option res_near_tangent

Option res_near_tangent specifies the largest angle in radians that is considered tangent. This option is a system-wide setting for the tolerance to use in testing whether or not an edge is considered tangent (based on the angle between normals). Tolerant modeling algorithms throughout the system may use this value. This option may be used in conjunction with other options that control specific tolerant modeling functionality. For example, this option has no effect on local operations and shelling when lop_tolerant_hot is FALSE.

The value is specified in radians, with a logical range of 0.0 to 2pi. In practice, this will be a small number close to zero.

Option lop_tolerant_hot

Local operations and shelling are only able to create new tolerant geometry when option lop_tolerant_hot is TRUE. Offsetting and shelling create near-tangent tolerant edges in each of the following cases:

A tolerant edge or a non-tangent edge has its convexity flag marked "tangent." (Algorithms such as blending, lofting, and sweeping will set the convexity flag to "tangent" on edges that the algorithm intended to be tangent, whether tangency is achieved to ACIS tolerances or not.)
The edge is not tangent but the angle between the surfaces along the edge is less than the value contained in res_near_tangent.

By treating near-tangent edges as tangent, difficult intersections that are likely to be slow and/or fail are avoided between near coincident surfaces.

Option bl_tolerant_hot

The tolerant modeling hot features of blending may be enabled by setting the option bl_tolerant_hot to TRUE. Unless this option is turned on, the blending algorithms will never create a tolerant edge if none was encountered on the blank, even if difficult near-tangencies are involved.