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IDProjectCategoryView StatusDate SubmittedLast Update
0031195Open CASCADE[OCCT] PRODUCTS:PMI Visualizationpublic2019-11-25 13:392019-11-25 14:05
Assigned Tonds 
PlatformOSOS Version
Product Version 
Target Version[OCCT] 7.5.0*Fixed in Version 
Summary0031195: PMIVis - angle dimension semantic
DescriptionIt's proposed to implement the following combination of geometry for angle:

1. between two segments/lines without crossing, where:
    A segment is a model/mesh edge
    A line is a circle/cylinder axis
2. between plane and segment/line
3. between two planes, where a plane is a planar model face or a mesh element
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-  Notes
nds (developer)
2019-11-25 14:04

There is very limited number of geometry combination to compute semantic presentation of angle defined by referenced shapes: linear edge-edge, face-face, face of revolution.

Some of customer files contain a combination of a b-spline surface and a circular surface. This case is expected to be processed.

The semantic computation was estimated by AZV. The following improvement is proposed:
The first approach is to find two points (one on each surface). After that, calculate the third point somewhere in 3D space to compose the required value of the angle dimension. This approach is pretty simple for implementation but it has several disadvantages:
• it does not provide the correct dimension, because the real angle between the surfaces in the reference points may be different;
• the position of the dimension will be related to the reference points, so, it should be correctly specified for each type of the surface how the reference point is taken.

Another approach will give the correct result taking into account the type of the referenced surfaces. The angle between surfaces will be calculated according to the characteristic direction:
• normal direction for a planar surface (implemented);
• axis of revolution for a cylinder, cone, torus or surface of revolution (partially implemented);
• direction for a surface of extrusion;
• normal for all other types of surfaces (sphere, Bezier, B-spline, etc.).
Searching the reference point on the elementary surface is not a problem. The main complexity is related to B-spline and Bezier surfaces. Searching the reference point in these cases, if the other surface is elementary, will be the following:
• calculate normal directions in each B-spline/Bezier knot;
• find the most appropriate span taking into account the angle between the normals in its corners and the reference direction of another surface (the calculated range of angles should contain the given dimension value);
• run Newton optimization to find the reference point within the span.
In case of the angle dimension is set between a pair of non-elementary surfaces, the algorithm will compare angle ranges on pairs of spans (one for each surface) and then select the most appropriate pair.

- Issue History
Date Modified Username Field Change
2019-11-25 13:39 nds New Issue
2019-11-25 13:39 nds Assigned To => nds
2019-11-25 13:40 nds Relationship added related to 0031194
2019-11-25 14:04 nds Note Added: 0089202

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