CREATEPTS/SPHERE

Builds a sphere by generating coordinates of points and also modifies zoning by ratio-zoning point distributions. See the rz command for more details.

Use connect to generate tet or triangle connectivity for all types except option 8 which generates the hex connectivity.

SYNTAX

createpts /sphere / itype / nr,npt,xirad,xorad / xcen,ycen,zcen / iz / irat,rz

Types for sphere itype:

  • 1 generates a sphere by gridding the faces of a cube and then projecting the vertices onto a sphere. The number of nodes per shell is of the form 6*i**2.

  • 2 generates a sphere by subdividing an icosahedron placed on the surface of a sphere. Icosahedral gridding is made up of 10 diamonds per shell. Each diamond is made up of n**2 nodes (where n must be of the form 2**i+1). There are 2 nodes (the poles of the sphere) at which 5 diamonds meet and 10 nodes where 3 diamonds meet; hence there are a minimum of 12 nodes per shell. The number of nodes per shell can be 12, 42, 162, 642,…etc.

  • 8 generates a hexahedral icosahedron grid. This option distributes points and generates the grid connectivity data structures. This option does not require a connect command.

  • diamond generates the points for one diamond of the icosahedron.

Options:

nr is the number of radial shells

npt is the upper limit of the number of points in a shell, the number of points generated will be less than or equal to this number.

xirad , xorad are the inner and outer radii of the sphere. For itype =8 reverse inner and outer radii.

xcen, ycen, zcen are the coordinates of the center of the sphere

iz  if =0 then mins and maxs are used as cell centers, if =1 then mins and maxs are used as cell vertices

irat is ratio zoning switch (0=off,1=on)

rz is ratio zoning value - distance is multiplied by the value for each subsequent point.

EXAMPLES

createpts/sphere/8/5/162/1.0,0.5/0.,0.,0./1,0,0.0/
createpts/sphere/2/5/162/0.5,1.0/0.,0.,0./1,0,0.0/
createpts/sphere/diamond/5/162/1,.5/0,0,0/1,0,0/

Various spherical point distributions.

cmo / create / motet_sph
createpts/sphere/1/5/162/1.0,0.5/0.,0.,0./1,0,0.0/ 
cmo / setatt / motet_sph / imt / 1 0 0 / 1
filter / 1 0 0 
rmpoint / compress
connect

Projected cube onto a sphere connected into tets (Image clipped at half)
Number of nodes = 750 Number of elements = 4175

cmo / create / motet_sph
createpts/sphere/2/5/162/1.0,0.5/0.,0.,0./1,0,0.0/ 
cmo / setatt / motet_sph / imt / 1 0 0 / 1
filter / 1 0 0 
rmpoint / compress
connect

Icosohedron tet sphere connected into tets (Image clipped at half)
Number of nodes = 812 Number of elements = 4187