Feature: Optional scale and rotation arguments for SaveAsWexBim

[miseifert]

The SaveAsWexBim method already allowed for translation but not for an optional scaling and rotation.

The scaling has to be a scalar value because otherwise the value for OneMeter that is written to the file would be ambiguous.

---

The use-case here is that I want to scale a model to meters and re-apply the rotation (that I lost because I also need to set adjustWcs: true because it has a large offset placement and it's in millimeters) before I display it in the browser, together with other models.

But it feels impossible to get a rotation and scale applied without a change in the library itself (or re-implementing the SaveAsWexBim logic myself)

Basically what I want to do in my code is something along these lines:

using (var model = IfcStore.Open(fileName))
{
	var context = new Xbim3DModelContext(model);
	context.CreateContext(adjustWcs: true);  // without adjusting the geometry loses a lot of precision because of floating-point precision...

	// Get the matrix representing the placement if we didn't have adjustWcs
	var originalPlacement = model.Instances.OfType<IIfcLocalPlacement>(activate: true)
		.Where(lp => lp.PlacementRelTo == null)
		.Single()
		.RelativePlacement
		.ToMatrix3D();
	var rotation = originalPlacement.GetRotationQuaternion();  // get the rotation part
	var customScale = model.ModelFactors.LengthToMetresConversionFactor;
		
	var wexBimFilename = Path.ChangeExtension(fileName, "wexBIM");
	using (var wexBiMfile = File.Create(wexBimFilename))
	using (var wexBimBinaryWriter = new BinaryWriter(wexBiMfile))
	{
		model.SaveAsWexBim(wexBimBinaryWriter, scale: customScale, rotation: rotation);
		wexBimBinaryWriter.Close();
	}
	wexBiMfile.Close();
}

---

Sorry, I totally missed the part in the contributor guidelines that I should create an issue first. After the work I put in the commit and PR description I thought I will try it with the PR (and this apology 🙏 ). That's my bad and if you want to gauge the interest with an issue first please let me know and I will close the PR and open an issue instead.

[andyward]

Thanks for this - and the update. It looks sensible non-breaking and green lights on tests is good news. I've added one minor review item. I'd like @martin1cerny to review for any WCS / wexbim Region issues as that's his domain. Other than than good to merge. Cheers!

[martin1cerny]

Thank you for the contribution @miseifert. It is much appreciated!