Project Location

You can use these properties to construct a transform between the default Revit coordinates and the actual coordinates in the project:

// Obtain a rotation transform for the angle about true north
Transform rotationTransform = Transform.get_Rotation(
  XYZ.Zero, XYZ.BasisZ, project_north_angle );
 
// Obtain a translation vector for the offsets
XYZ translationVector = new XYZ(
  projectPosition.EastWest,
  projectPosition.NorthSouth,
  projectPosition.Elevation );
 
Transform translationTransform
  = Transform.get_Translation(
    translationVector );
 
// Combine the transforms into one.
Transform finalTransform
  = translationTransform.Multiply(
    rotationTransform );

South Facing Elements Using Project Location

In this example we adapt the

south-facing walls and

south-facing windows examples
to deal with a project where true north is not aligned with the Revit coordinate system.
The facing vectors are rotated by the angle from true north before the calculation is run, and the following walls are now determined to be south facing:

The following windows are now facing south:

Here is the method TransformByProjectLocation that we use to transform a direction vector by the rotation angle of the ActiveProjectLocation.
It takes a given normalized direction as an input argument and returns the transformed location:

protected XYZ TransformByProjectLocation(
  XYZ direction )
{
  // Obtain the active project location's position.
 
  ProjectPosition position
    = Document.ActiveProjectLocation.get_ProjectPosition(
      XYZ.Zero );
 
  // Construct a rotation transform from the position angle.
 
  Transform transform = Transform.get_Rotation(
    XYZ.Zero, XYZ.BasisZ, position.Angle );
 
  // Rotate the input direction by the transform
  XYZ rotatedDirection = transform.OfVector( direction );
 
  return rotatedDirection;
}

Please refer to Scott’s

AU class material for
the full source code of his sample project.

We will continue this series with a look at the powerful FindReferencesByDirection method coming up next.