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IDProjectCategoryView StatusLast Update
0033623CommunityOCCT:Data Exchangepublic2024-04-22 14:10
Reporterrobertlipman Assigned Toichesnokova  
Status assignedResolutionopen 
Product Version7.8.0 
Target Version7.8.2 
Summary0033623: Data Exchange, Step Import - STEP tessellated geometry not reading
DescriptionWe have built a new version of the NIST software that converts STEP to x3d with OCCT 7.8.0. Unexpectedly, it seems like 7.8.0 processes STEP AP242 tessellated geometry. It works well in most cases.

One case where it does not work is if triangulated_face is used instead of complex_triangulated_face. triangulated_face is not associated with any b-rep surfaces.

Attached are two examples.

We don't know if there are any settings that need to be used or if OCCT 7.8.0 just does not handle this case.
Steps To ReproduceSee if the tessellated geometry can be processed from the files.
TagsNo tags attached.
Test case number

Attached Files

  • rook-stl.stp (94,183 bytes)


duplicate of 0029241 verifiedbugmaster Open CASCADE Data Exchange - Empty shape after reading STEP file. 
related to 0033410 verifiedvglukhik Community Data Exchange, Step Import - TRIANGULATED_FACE from STEP where there are no pnval entries 



2024-03-01 22:45

administrator   ~0115212

Dear @robertlipman, please check the attachments.
We have some problems with attachments in creating ticket time (they can be skipped)


2024-03-01 23:04

administrator   ~0115218

Just for information, we have plans for x3d opensource reader and writer. As the next stage of VRML format.


2024-03-18 18:12

administrator   ~0115413

Files recieved.


2024-04-19 23:09

developer   ~0115754

Hello @robertlipman.
If we rely on recommended practices ( chapter 5.3), pnindex array for triangulated_face should contains indices of coordinate_list. But in rook-stl.stp file pnindex contains invalid indices.
So it seems that the file doesn't correspond to the recommended practices. Could you please share, how the file was exported?


2024-04-20 00:48

reporter   ~0115756

The file is created by the NIST software that converts an STL file to AP242 tessellated geometry. STL defines normals per face, however, in STEP normals are applied to coordinates, therefore there is a bug in my software. Attached is a fixed file where no normals are defined. Now pnmax=0, and both the normals and pnmax attributes are set to (). The only items defining the tessellated geometry are the coordinates_list and the triangles attribute on triangulated_face. The file was checked with conformance checking software and there are no problems.
rook-stl.stp (94,183 bytes)

Issue History

Date Modified Username Field Change
2024-03-01 20:05 robertlipman New Issue
2024-03-01 20:05 robertlipman Assigned To => ika
2024-03-01 22:41 dpasukhi Summary STEP tessellated geometry not reading => Data Exchange, Step Import - STEP tessellated geometry not reading
2024-03-01 22:45 dpasukhi Target Version => 7.8.1
2024-03-01 22:45 dpasukhi Note Added: 0115212
2024-03-01 22:51 dpasukhi Assigned To ika => dpasukhi
2024-03-01 22:53 dpasukhi Relationship added related to 0033410
2024-03-01 23:04 dpasukhi Note Added: 0115218
2024-03-18 18:12 dpasukhi Note Added: 0115413
2024-03-18 18:12 dpasukhi Assigned To dpasukhi => ichesnokova
2024-03-18 18:12 dpasukhi Status new => assigned
2024-03-18 18:17 dpasukhi Relationship added duplicate of 0029241
2024-04-19 23:09 ichesnokova Note Added: 0115754
2024-04-20 00:48 robertlipman Note Added: 0115756
2024-04-20 00:48 robertlipman File Added: rook-stl.stp
2024-04-22 14:10 dpasukhi Target Version 7.8.1 => 7.8.2