[Bug]: Non-manifold geometry triangulation

[kersh1337228]

What happened?

Short description:

Non-manifold meshes are returned by GetGeometry() function althought ones must be manifold.
Non-manifold here means mesh has more than 2 triangles per edge (4 in model attached).

Detailed description:

Calculating volumes of triangulated meshes is quite straightforward when next conditions are satisfied:

• manifold;
• closed;
• consistently oriented indices (no normals flipped).

Then volume can be easily calculated using signed volumes method.

Calculating volume using this approach succeeds when meshes given are manifold: in this case the result using manual calculation and BIMVision matches exactly. However there are meshes in model given which appear to be non-manifold when loaded using GetGeometry() function and manifold while loaded by BIMVision (BIMVision calculates volume successfully while manually inspecting mesh loaded using GetGeometry() shows it is non manifold).

Here is an example for model attached that you can easily check yourself:

• use GetGeometry on line with id 557526;
• check if geometry returned is manifold (whether edges with more than 2 triangles exist);

4 triangles for 1 edge are (<triangle index>: <vertices coordinates>):

431: [
    [3.30261492729187, 10.859160423278809, -1.1873899698257446],
    [3.658644914627075, 10.574810028076172, -1.1674100160598755],
    [8.253544807434082, 6.904950141906738, -0.7966499924659729]
],
430: [
    [3.658644914627075, 10.574810028076172, -1.1674100160598755],
    [1.7518450021743774, 12.097729682922363, -1.1707700490951538],
    [3.30261492729187, 10.859160423278809, -1.1873899698257446]
],
403: [
    [3.30261492729187, 10.859160423278809, -1.1873899698257446],
    [3.658644914627075, 10.574810028076172, -1.1674100160598755],
    [3.403404951095581, 10.222060203552246, -1.1777900457382202]
],
432: [
    [4.005034923553467, 10.298150062561035, -1.165719985961914],
    [3.658644914627075, 10.574810028076172, -1.1674100160598755],
    [3.30261492729187, 10.859160423278809, -1.1873899698257446]
]

Common edge here is obviously:

[
    [3.30261492729187, 10.859160423278809, -1.1873899698257446],
    [3.658644914627075, 10.574810028076172, -1.1674100160598755]
]

Version

0.0.57

What browsers are you seeing the problem on?

Chrome

Relevant log output

No response

Anything else?

Problematic model

Screenshot of geometry mentioned in example (left - manual calculation, right - BIMVision):