subroutine aptcube (vx, vy, vz, nv1, nv2)

ccbeg.
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c
c                             SUBROUTINE APTCUBE
c
c     call aptcube (vx, vy, vz, nv1, nv2)
c
c     Version:  aptcube  Updated    1990 March 12 13:10.
c               aptcube  Originated 1989 November 2 14:10.
c
c     Author:   Arthur L. Edwards, LLNL, L-298, Telephone (925) 422-4123.
c
c
c     Purpose:  To generate a regular cube inscribed in a unit sphere.
c               A cube has 8 vertices, 12 edges, and 6 square faces.
c               Edges join vertex pairs 1-2, 1-4, 1-5, 2-3, 2-6, 3-4, 3-7,
c               4-8, 5-6, 5-8, 6-7, 7-8.
c               Vertices 1 and 7 are on the z axis.
c               Edge 1-2 is from (0, 0, 1) to (2*sqrt(2)/3, 0, 1/3).
c
c     Input:    None
c
c     Output:   (vx(nv), vy(nv), vz(nv), nv = 1, 8),
c               (nv1(ne), nv2(ne), ne = 1, 12).
c
c     Note:     See aptdode to generate a regular dodecahedron.
c               See apticos to generate a regular icosahedron.
c               See apttetr to generate a regular tetrahedron.
c               See aptocta to generate an octahedron with the same symmetry.
c
c     Glossary:
c
c     nv1       Output   Index of first vertex of edge ne.  Size 12.
c
c     nv2       Output   Index of second vertex of edge ne.  Size 12.
c
c     vx,vy,vz  Output   The x, y, z coordinates of a vertex of a cube.
c                          (A regular hexahedron.)  Size 8.
c
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ccend.

c.... Dimensioned arguments.

c---- Index of first vertex of edge.
      dimension nv1     (12)
c---- Index of second vertex of edge.
      dimension nv2     (12)

c---- Coordinate x of cube vertex.
      dimension vx      (8)
c---- Coordinate y of cube vertex.
      dimension vy      (8)
c---- Coordinate z of cube vertex.
      dimension vz      (8)

c.... Local variables.

c---- Index of edge.
      common /laptcube/ ne
c---- Index of first vertex of edge.
      dimension nver1   (12)
c---- Index of second vertex of edge.
      dimension nver2   (12)

      data (nver1(n), n = 1, 12) /1, 1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 7/
      data (nver2(n), n = 1, 12) /2, 4, 5, 3, 6, 4, 7, 8, 6, 8, 7, 8/
cbugc***DEBUG begins.
cbugc---- Dihedral angle.
cbug      common /laptcube/ alpha
cbugc---- Face area.
cbug      common /laptcube/ area
cbugc---- Total face area.
cbug      common /laptcube/ areatot
cbugc---- Edge length.
cbug      common /laptcube/ dl1
cbugc---- Edge length squared.
cbug      common /laptcube/ dl2
cbugc---- Edge length cubed.
cbug      common /laptcube/ dl3
cbugc---- Index in vx, vy, vz.
cbug      common /laptcube/ n
cbugc---- Error flag from rotax.
cbug      common /laptcube/ nerr
cbugc---- Central angle of edge.
cbug      common /laptcube/ phi
cbugc---- Mathematical constant, pi.
cbug      common /laptcube/ pi
cbugc---- Mathematical constant, pi.
cbug      data pi /3.14159265358979323/
cbugc---- Rotation matrix.
cbug      common /laptcube/ rotm   (3,3)
cbugc---- Inscribed sphere radius.
cbug      common /laptcube/ rs1
cbugc---- Inscibed sphere radius squared.
cbug      common /laptcube/ rs2
cbugc---- Inscribed sphere radius cubed.
cbug      common /laptcube/ rs3
cbugc---- Volume.
cbug      common /laptcube/ volume
cbugc***DEBUG ends.

c.... Generate the 8 vertices of a regular cube.
c....   Orientation is symmetric with the regular tetrahedron
c....   generated by apttetr.  Vertices 1 and 7 on z axis.
c....   Orientation is symmetric with the octahedron generated by aptocta.

      vx(1) =  0.0
      vy(1) =  0.0
      vz(1) =  1.0

      vx(2) =  2.0 * sqrt (2.0) / 3.0
      vy(2) =  vy(1)
      vz(2) =  1.0 / 3.0

      vx(3) =  sqrt (2.0) / 3.0
      vy(3) =  sqrt (6.0) / 3.0
      vz(3) = -vz(2)

      vx(4) = -vx(3)
      vy(4) =  vy(3)
      vz(4) =  vz(2)

      vx(5) = -vx(3)
      vy(5) = -vy(3)
      vz(5) =  vz(2)

      vx(6) =  vx(3)
      vy(6) = -vy(3)
      vz(6) = -vz(2)

      vx(7) =  vx(1)
      vy(7) =  vy(1)
      vz(7) = -vz(1)

      vx(8) = -vx(2)
      vy(8) =  vy(1)
      vz(8) = -vz(2)

c.... Generate the indices of the vertices bounding each edge.

      do 110 ne = 1, 12
        nv1(ne) = nver1(ne)
        nv2(ne) = nver2(ne)
  110 continue
cbugc***DEBUG begins.
cbug 9901 format (// 'cube vertices.' //
cbug     &  '  n    x',15x,'y',15x,'z')
cbug 9902 format (i3,3f16.12)
cbug 9903 format (/ 'Edges:' /
cbug     &  (2i3))
cbug      write ( 3, 9901)
cbug      write ( 3, 9902) (n, vx(n), vy(n), vz(n), n = 1, 8)
cbug      write ( 3, 9903) (nv1(n), nv2(n), n = 1, 12)
cbug      write ( 3, '(//)')
cbug
cbugc____     call plotpoly (8, vx, vy, vz, 12, nv1, nv2)
cbugc____     call rotax (8, vx, vy, vz, 1.0, 1.0, 1.0, 0, 30.0, rotm, nerr)
cbugc____     call plotpoly (8, vx, vy, vz, 12, nv1, nv2)
cbug
cbug      dl1 = 2.0 / sqrt (3.0)
cbug      dl2 = dl1**2
cbug      dl3 = dl1 * dl2
cbug      rs1 = 1.0 / sqrt (3.0)
cbug      rs2 = rs1**2
cbug      rs3 = rs1 * rs2
cbug      area = 4.0 / 3.0
cbug      areatot = 6.0 * area
cbug      volume = 8.0 * sqrt (3.0) / 9.0
cbug      alpha = acos (0.0) * 180.0 / pi
cbug      phi = acos (1.0 / 3.0) * 180.0 / pi
cbug 9904 format ('  dl, dl**2, dl**3=',1p3e20.12 /
cbug     &  '  r, r**2, r**3=',1p3e20.12 /
cbug     &  '  area=',1pe20.12,'  areatot=',1pe20.12 /
cbug     &  '  volume=',1pe20.12 /
cbug     &  '  alpha=',1pe20.12,'  phi=',1pe20.12)
cbug      write ( 3, 9904) dl1, dl2, dl3, rs1, rs2, rs3, area, areatot,
cbug     &  volume, alpha, phi
cbugc***DEBUG ends.

      return

c.... End of subroutine aptcube.      (+1 line.)
      end

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