It is up to you how to interpret values of coordinates, mm, inch, m or something else. However, when you import/export IGES or STEP format, you can define the current units. To get better result of algorithms connected with intersector, I think it's better when dimensions of shapes are from ones to the thousands, and small features like holes and bendings being not smaller than 0.01.
Archived discussion
What units does Open CASCADE use?
I am writing some CAD/CAM software.
Is it OK to use code like gp_Pnt(25.0, 0.0, 0.0) with 25.0mm?
And if I am using inches should I use gp_Pnt(1.0, 0.0, 0.0) for inches?
Or should everything be in metres?
Do functions like BRepAlgoAPI_Cut work better with big geometry or small geometry?
Discussion
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Thanks Bearloga,
I have used Parasolid at work, where they say that all units must be in metres.
I am planning on making my software in millimetres, so I have started by giving Open CASCADE millimetres.
It seems OK so far. I have done a few boolean operations with some primitives and with some STEP files.
So, I'll stay with millimetres until I find out differently.
I can't believe this is stuff is free!
Hello Bearloga,
I have a STEP file ( say in mm) and in my INCH system which I use OCC, I want to convert the imported geometry into INCH units.
Any tips in this regard - i scanned through lot of old forum threads
regards
-PG
Read STEP User's Guide, page 11: you need to set parameter xstep.cascade.unit