ImportStep does not respect unit

[Steinblock]

I have a simple step file and CADability shows the width and height as 0.38 and 0.8.

However the part has been constructed in Autodesk Inventor 2023 and saved with unit meter. Other step viewers show the correct size of 380 and 800.

Here is the file for reference.

simple-part-mm.zip

[dsn27]

It seems like the unit is not read under all circumstances.
While there is code that is trying to figure out the units, this does not seem to work for this file.
e.g.

CADability/CADability/ImportStep.cs

Lines 4757 to 4782 in e6794d6

	private double GetContextLengthFactor(Item item)
	{
	Item units = item.parameter["units"];
	if (units != null && units.type == Item.ItemType.list)
	{
	foreach (Item it in units.val as List<Item>)
	{
	if (it.parameter.TryGetValue("conversion_factor", out Item cf))
	{
	if (cf.parameter.TryGetValue("value_component", out Item vc))
	{
	if (cf.type == Item.ItemType.lengthMeasureWithUnit && vc.val is List<Item> && (vc.val as List<Item>)[0].type == Item.ItemType.floatval)
	{
	double f = (vc.val as List<Item>)[0].fval;
	if (cf.parameter.TryGetValue("unit_component", out Item uc))
	{
	}
	return f; // * 1000; // why * 1000.0 ??? definitely wrong with AM3024-0x00.stp
	}
	}
	}
	}
	}
	return 1.0;
	}

CADability/CADability/ImportStep.cs

Lines 4804 to 4825 in e6794d6

	if (item.parameter.TryGetValue("units", out Item units) && units.type == Item.ItemType.list)
	{
	foreach (Item it in units.val as List<Item>)
	{
	if (it.parameter.TryGetValue("conversion_factor", out Item cf))
	{
	if (cf.parameter.TryGetValue("value_component", out Item vc))
	{
	if ((cf.type == Item.ItemType.planeAngleMeasure || cf.type == Item.ItemType.planeAngleMeasureWithUnit) && vc.val is List<Item> && (vc.val as List<Item>)[0].type == Item.ItemType.floatval)
	context.toRadian = (double)(vc.val as List<Item>)[0].val;
	if ((cf.type == Item.ItemType.positiveLengthMeasure || cf.type == Item.ItemType.lengthMeasureWithUnit) && vc.val is List<Item> && (vc.val as List<Item>)[0].type == Item.ItemType.floatval)
	{
	context.factor = (double)(vc.val as List<Item>)[0].val; // why * 1000 ? definitely wrong for 83855_elp11b.stp
	if (it.parameter.TryGetValue("name", out Item name))
	{
	if (name.type == Item.ItemType.stringval && name.sval == "METRE") context.factor *= 1000; // added because of "PROBLEM ELE NULLPUNKT.stp"
	}
	}
	}
	}
	}
	}

[dsn27]

The original code is looking for "conversion_factor" and "value_component" inside a Units Items.

But it looks like in issue153.stp the unit is available at top level and we just need to read it.

Remarks:
We should add support for other Units and check the old code.
Why is the factor always multiplied by 1000?
What happens if this code is called multiple times?

CADability/CADability/ImportStep.cs

Lines 4819 to 4820 in e6794d6

	if (name.type == Item.ItemType.stringval && name.sval == "METRE") context.factor *= 1000; // added because of "PROBLEM ELE NULLPUNKT.stp"
	}

We would need several STEP files that trigger this code path to check on this.

[dsn27]

Closed by #182