public static bool TryGetExtrusion(this Brep brep, out Extrusion extrusion)
{
if (brep.IsSurface)
{
return(brep.Faces[0].TryGetExtrusion(out extrusion));
}
extrusion = null;
if (brep.Faces.Count < 3)
{
return(false);
}
// Requiere manifold breps
if (brep.SolidOrientation == BrepSolidOrientation.None || brep.SolidOrientation == BrepSolidOrientation.Unknown)
{
return(false);
}
// If brep has more that 3 faces we should check if there are faces with interior loops
if (brep.Faces.Count > 3 && brep.Faces.Where(face => face.Loops.Count != 1).Any())
{
return(false);
}
var candidateFaces = new List <int[]>();
// Array with just planar faces sorted by its area to search for similar faces
var planarFaces = brep.Faces.
Select(face => new PlanarBrepFace(face)).
Where(face => face.Plane.IsValid).
OrderByDescending(face => face.LoopArea).
ToArray();
// A capped Extrusion converted to Brep has wall surfaces in face[0] to face[N-3], caps are face[N-2] and face[N-1]
// I iterate in reverse order to be optimisitc, maybe brep comes from an Extrusion.ToBrep() call
for (int f = planarFaces.Length - 1; f > 0; --f)
{
var planeF = planarFaces[f].Plane;
var loopF = planarFaces[f].Loop;
var centroidF = planarFaces[f].Centroid;
// Check if they have same area.
for (int g = f - 1; g >= 0 && RhinoMath.EpsilonEquals(planarFaces[f].LoopArea, planarFaces[g].LoopArea, RhinoMath.SqrtEpsilon); --g)
{
// Planes should be parallel or anti-parallel
if (planeF.Normal.IsParallelTo(planarFaces[g].Plane.Normal, RhinoMath.DefaultAngleTolerance / 100.0) == 0)
{
continue;
}
// Here f, and g are perfect candidates to test adjacent faces for perpendicularity to them,
// but we may try to quick reject some candidates if it's obvious that doesn't match
// A "perfect" curve overlap match may be a test but is too much in this ocasion
// We expect same NURBS structure, so point count should match
if (loopF.Points.Count != planarFaces[g].Loop.Points.Count)
{
continue;
}
// Since we have computed the area the centroid comes for free.
// Centroids should also match
if (planeF.ClosestPoint(planarFaces[g].Centroid).DistanceToSquared(centroidF) > RhinoMath.SqrtEpsilon)
{
continue;
}
// Add result to candidates List reversing index order to keep extrusion creation direction
// Breps that come from a Extrusion have the Cap[0] before Cap[1]
candidateFaces.Add(new int[] { g, f });
}
}
// No twin faces found
if (candidateFaces.Count == 0)
{
return(false);
}
// Candidates are in 'LoopArea' order, we will find here smaller profiles sooner
// This is good for beam like objects, bad for slab like objects.
// On box-like Breps the result could be ambigous for the user so,
// to give him some control on the result, we will prioritize first and last faces no matter their area.
// First and Last are "special" because if somebody observe an extrusion-like Brep and sees
// it as an extrusion he tends to categorize faces in one of the following schemas:
// { Cap[0], Wall[0] .. Wall[N], Cap[1] }
// { Cap[0], Cap[1], Wall[0] .. Wall[N] }
// { Wall[0] .. Wall[N], Cap[0], Cap[1] }
// So if he is using the join command to create a Brep from surfaces at the model,
// it's natural to start or end the selection with one of the extrusion caps.
// On horizontal extrusions, slab-like Breps, the user use to observe the model from above,
// so probably he will end with the bottom cap.
// Also Last face is a Cap in Breps that come from Extrusion
// If caps and walls are interleaved, smallest pair of faces will be used as caps, producing beam-like extrusions.
// System.Linq.Enumerable.OrderBy performs a stable sort so only first and last face will be moved if found.
foreach (var candidate in candidateFaces.OrderBy(pair => (planarFaces[pair[1]].Face.FaceIndex == brep.Faces.Count - 1) ? 0 : // Last, in case it comes from Extrusion
(planarFaces[pair[0]].Face.FaceIndex == 0) ? 1 : // First, in case it comes from a JOIN command
int.MaxValue)) // Others
{
var startFace = planarFaces[candidate[0]];
var endFace = planarFaces[candidate[1]];
// If any face, ignorig twins candidates, does not degenrate
// to a curve when projected to 'planeF', then brep is not an extrusion
if
(
brep.Faces.
Where(face => face.FaceIndex != startFace.Face.FaceIndex && face.FaceIndex != endFace.Face.FaceIndex).
Select(face => startFace.ProjectionDegenartesToCurve(face.UnderlyingSurface())).
Any(degenerateToCurve => degenerateToCurve == false)
)
{
return(false);
}
// We use the orginal OuterLoop as profile not the NURBS version of it
// to keep the structure as much as possible
var profile = startFace.Face.OuterLoop.To3dCurve();
double height = startFace.Face.OrientationIsReversed ?
-startFace.Plane.DistanceTo(endFace.Plane.Origin) :
+startFace.Plane.DistanceTo(endFace.Plane.Origin);
extrusion = Extrusion.Create(profile, height, true);
return(extrusion is object);
}
return(false);
}
