Fixing Incorrect STEP File Linear Units - Idea 2

See also:  Idea 1 for fixing a STEP file.

How Wrong Scales in STEP Files Affect VTube

After importing a STEP model of a tube, if you attempt to calculate a centerline and find that the calculation takes much longer than usual and the resulting values are huge, then there is probably a problem in the original STEP file setup for linear units.
 

In this example of incorrect STEP file linear units, all distances were 1000 times too large.

In a sample file shared with us, the partial data in the file looks like this:

RPRCNT('DIR23F105_REVA','TOP_LEVEL_ASSEMBLY_PART')
);
#448=UMWU(LENGTH_MEASURE(7.8740157480315E-7),#453,
'DISTANCE_ACCURACY_VALUE','Maximum Tolerance applied to model');
#449=(
NMDUNT(*)
SUNT($,.STERADIAN.)
SLANUN()
);
#450=(
CNBSUN('DEGREE',#451)
NMDUNT(#455)
PLANUN()
);
#451=PAMWU(PLANE_ANGLE_MEASURE(0.0174532925),#452);
#452=(
NMDUNT(*)
PLANUN()
SUNT($,.RADIAN.)
);
#453=(
CNBSUN('INCH',#456)
LNGUNT()
NMDUNT(#454)
);
#454=DMNEXP(1.,0.,0.,0.,0.,0.,0.);
#455=DMNEXP(0.,0.,0.,0.,0.,0.,0.);
#456=LMWU(LENGTH_MEASURE(25.4),#457);
#457=(
LNGUNT()
NMDUNT(*)
SUNT(.MILLI.,.METRE.)
);
ENDSEC;
END-ISO-10303-21;

Look for the LENGTH_MEASURE field with any metric-to-inch conversion value - like "25.4".

Change

#456=LMWU(LENGTH_MEASURE(25.4),#457);

to

#456=LMWU(LENGTH_MEASURE(0.0254),#457);

then import the file again. The linear units are fixed.

The goal is to adjust the value by a factor of 1000 until the incoming data is imported correctly in VTube-STEP.

After a STEP import, you can move the mouse pointer across the viewport to see if the XYZ position values on the bottom of the viewport are reasonable to confirm that you have fixed the problem.

See also:  Idea 1 for fixing a STEP file.