// GetShapeNurbs returns a shape structure based on NURBS
// Note: span are the local ids of control points in NURBS defining elements
// Note: FaceLocalVerts does not work for internal surfaces; only those @ boundaries
func GetShapeNurbs(nurbs *gm.Nurbs, nrbfaces []*gm.Nurbs, span []int) (o *Shape) {
// basic data
o = new(Shape)
o.Type = "nurbs"
o.FaceType = "nurbs"
o.Gndim = nurbs.Gnd()
switch o.Gndim {
case 1:
o.BasicType = "lin2"
case 2:
o.BasicType = "qua4"
case 3:
o.BasicType = "hex8"
}
o.Nverts = nurbs.GetElemNumBasis()
o.VtkCode = VTK_POLY_VERTEX
o.Func = o.NurbsFunc
o.FaceFunc = o.NurbsFaceFunc
o.Nurbs = nurbs
o.Span = span
o.Ibasis = o.Nurbs.IndBasis(o.Span)
o.U = make([]float64, o.Gndim)
// faces basic data
nfaces := 2 * o.Gndim
o.FaceLocalVerts = nurbs.ElemBryLocalInds()
if o.Gndim == 3 {
o.NurbsFaces = nrbfaces
o.SpanFace = [][]int{
span[0:2], span[0:2],
span[2:4], span[2:4],
span[4:6], span[4:6],
}
o.FaceFlip = []bool{false, true, false, true, false, true} // => point to the inside
} else {
o.NurbsFaces = []*gm.Nurbs{nrbfaces[2], nrbfaces[1], nrbfaces[3], nrbfaces[0]}
o.SpanFace = [][]int{span[0:2], span[2:4], span[0:2], span[2:4]}
o.FaceFlip = []bool{false, false, true, true} // => point to the inside
}
o.IbasisFace = make([][]int, nfaces)
for idxface, face := range o.NurbsFaces {
o.IbasisFace[idxface] = face.IndBasis(o.SpanFace[idxface])
if idxface == 0 {
o.FaceNvertsMax = len(o.IbasisFace[idxface])
} else {
o.FaceNvertsMax = utl.Imax(o.FaceNvertsMax, len(o.IbasisFace[idxface]))
}
}
// allocate stracthpad variables
o.init_scratchpad()
return
}
