/// <summary>
/// returns the area of the polyloop
/// </summary>
/// <param name="loop"></param>
/// <returns></returns>
public static double Area(this IfcPolyLoop loop)
{
XbimVector3D sum = new XbimVector3D(0, 0, 0);
IList<IfcCartesianPoint> pts = loop.Polygon;
for (int i = 0; i < pts.Count - 1; i++)
{
XbimVector3D a = new XbimVector3D(pts[i].X,pts[i].Y,pts[i].Z);
XbimVector3D b = new XbimVector3D(pts[i + 1].X, pts[i + 1].Y, pts[i + 1].Z);
sum = sum + a.CrossProduct(b);
}
XbimVector3D n = loop.NewellsNormal();
return n.DotProduct(sum) / 2;
}
// Two CreateRotation functions below are adapted from the implementation of getRotation in
// the VisualizationLibrary SDK (sources at http://visualizationlibrary.org/ )
/// <summary>
/// Creates a rotation matrix converting from a starting direction to a desired direction.
/// </summary>
/// <param name="fromDirection">Starting direction</param>
/// <param name="toDirection">Desired direction</param>
/// <returns>the matrix that applied to <see paramref="fromDirection"/> results in <see paramref="toDirection"/></returns>
public static XbimMatrix3D CreateRotation(XbimPoint3D fromDirection, XbimPoint3D toDirection)
{
var a = new XbimVector3D(toDirection.X, toDirection.Y, toDirection.Z);
var b = new XbimVector3D(fromDirection.X, fromDirection.Y, fromDirection.Z);
a = a.Normalized();
b = b.Normalized();
double cosa = a.DotProduct(b);
cosa = clamp(cosa, -1, +1);
var axis = XbimVector3D.CrossProduct(a, b).Normalized();
double alpha = Math.Acos(cosa);
return(CreateRotation(alpha, axis));
}
public static XbimMatrix3D CreateWorld(XbimVector3D position, XbimVector3D forward, XbimVector3D up)
{
// prepare vectors
forward.Normalized();
XbimVector3D vector = forward * -1;
XbimVector3D vector2 = XbimVector3D.CrossProduct(up, vector);
vector2.Normalized();
XbimVector3D vector3 = XbimVector3D.CrossProduct(vector, vector2);
// prepare matrix
XbimMatrix3D result = new XbimMatrix3D(
vector2.X, vector2.Y, vector2.Z, 0.0,
vector3.X, vector3.Y, vector3.Z, 0.0,
vector.X, vector.Y, vector.Z, 0.0,
position.X, position.Y, position.Z, 0.0);
return(result);
}
// Microsoft.Xna.Framework.Matrix
public static XbimMatrix3D CreateLookAt(XbimVector3D cameraPosition, XbimVector3D cameraTarget, XbimVector3D cameraUpVector)
{
// prepare vectors
XbimVector3D vector = cameraPosition - cameraTarget;
vector.Normalized();
XbimVector3D vector2 = XbimVector3D.CrossProduct(cameraUpVector, vector);
vector2.Normalized();
XbimVector3D vector3 = XbimVector3D.CrossProduct(vector, vector2);
// prepare matrix
XbimMatrix3D result = new XbimMatrix3D(
vector2.X, vector3.X, vector.X, 0.0,
vector2.Y, vector3.Y, vector.Y, 0.0,
vector2.Z, vector3.Z, vector.Z, 0.0,
-XbimVector3D.DotProduct(vector2, cameraPosition), -XbimVector3D.DotProduct(vector3, cameraPosition), -XbimVector3D.DotProduct(vector, cameraPosition), 1.0);
return(result);
}
public XbimVector3D CrossProduct(XbimVector3D v2)
{
return(XbimVector3D.CrossProduct(this, v2));
}
