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PDQ criteria
by Atsuto Soma
# PDQ criteria

## Detection of Faulty data

### Bad shape

### Redundant data

## Interpretation of
explicit condition

### Violation of
mathematical
representation

### Specification
of CAD

### Use case

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Specification shall bed determined a posteriori

Self-intersection, topology_related_to_self_intersecting_geometry, self_intersecting_geometry, Always erroneous in any application, Informal rule in Part 42

Small segment/patch, nearly degenerate segment or patch or boundary, indistinct curve/surface knots, nearly_degenerate_surface_boundary, short_length_curve_segment, small_area_surface_patch, narrow_surface_patch, nearly_degenerate_surface_patch, extreme_patch_width_variation, Maybe problematic for some systems, e.g. projecting curve onto the surface. Relatively narrow patch.

Bad condition of curve/surface normal, Normal value, zero_surface_normal, Always problematic when the zero normal location is evaluated. But some systems always create this for vertex region of fillet., surface_with_small_curvature_radius, curve_with_small_curvature_radius, Basically bad shape, but it's difficult to set threshold, Because it is not logically linked to system point coincident tolerance. -> That decreases severity of these criteria., Change of direction, steep_geometry_ transition_across_edge, steep_angle_between_adjacent_edges, steep_angle_between_adjacent_faces, abrupt_change_of_ surface_normal, Maybe problematic for some systems, e.g. projecting curve onto the surface

multiply_defined_*

overlapping_*

overcomplex_*

Specification can be explicitly determined from various conditions

erroneous_data

occurrence possibility is low

Severity is extremely high when occurred.

It's very rare to use these for data from stable systems

Some criteria are used for cleaning up very dirty data. In this case, experiment is needed to specify criteria to be used.

Restriction of mathematical representation, inapt_topology, excessively_high_degree_curve/surface, discontinuous_geometry, These criteria are to be automatically handled by data translator if possible, or checked just before translation.

Basic accuracy of CAD, nearly_degenerate_geometry, geometric_gap_in_topology, small_volume_solid and entirely_narrow_solid, Severity is high when occurred, Why not included in CAD specification dependent? -> criteria in "CAD specification dependent" arena is the ones to be handled in general data translator. And many CAD don't use fixed value., It is not easy, and sometimes undesirable to handle these criteria in data translator

non_smooth_geometry_transition_across_edge

inapt_topology