Wed, 04/09/2025 - 20:59
Hi, everybody.
Another misunderstanding of how it all works (
I'm using STEPCAFControl_Reader, and I want to use a specific XDE Label or TopoDS_Shape to find the associated StepGeom_Axis2Placement3d from a STEP file.
I don't understand how to do it, if it is possible at all.
If you look in the step file, there is an entity there #175 = AXIS2_PLACEMENT_3D('',#176,#177,#178) for example.
And I want to get that coordinate system.
Maybe you don't need to try to get it that way and you can get everything from the XDE level
The task is to get the base vectors, which are bound to a particular geometry, to be able, removing further transformations, to get the location of the geometry, which it had at the time of design - orientation along the main axis, additional axes, etc.
Wed, 04/09/2025 - 23:46
Hello. OCCT provide functionality to detect all connection with shapes and STP entities. Not all information is stored inside XCAF.
I totally not get your task. Do you want to extract "Supplimental geometry" or transformation? Or some geometry defitinition?
For example, if you want to extract supplimental geometry (MCS/PCS,CSW,CIP,CRP) in case of correct assembly manipulation it is one case, if you want to detect the axis of the cylinder - it is another, or location of the shape. First is not possibly by only XDE, need to manipulate STP model and XDE together, other can be done purely on XDE.
Best regards, Dmitrii.
Thu, 04/10/2025 - 00:36
Let me try to describe the problem )
Let's take a bolt for example. When it was modeled in Solidworks, it was placed along the main Z axis The other axes are orthogonal accordingly. In fact, in the step file, it is written exactly in AXIS2_PLACEMENT_3D (you can get the local coordinate system from it).
Then, when this bolt was placed in the assembly and somehow positioned in space, a transformation was applied to this local coordinate system. I need to get this coordinate system without transformations. That is, to find how the major axis is directed relative to the minor axes in geometry without transformations.
Thu, 04/10/2025 - 01:51
Then you can follow the guide: Open CASCADE Technology: Extended Data Exchange (XDE)
You need to extract part and instance locations. That is what you are looking for.