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// some functions for the interpolation demo
function [xf,yf,zf,qf] = nf3dq(x,y,z,q,orient)
//
// same than nf3d but with a supplementary val field
//
// j+1 +----+ orient=1 corresponds to :
// | | (i,j) -> (i,j+1) -> (i+1,j+1) -> (i+1,j)
// j +----+
// i i+1 orient=2 corresponds to :
// (i,j) -> (i+1,j) -> (i+1,j+1) -> (i,j+1)
//
if ~exists("orient","local") then, orient=2, end
[n1,n2]=size(x)
nx = (n1-1)*(n2-1);
v = 1:(n1*n2-n1-1); v(n1*(1:(n2-2)))=[];
if orient == 1 then
ind = [v; v+n1; v+(n1+1); v+1];
else
ind = [v; v+1; v+(n1+1); v+n1];
end
xf=matrix(x(ind),4,nx)
yf=matrix(y(ind),4,nx)
zf=matrix(z(ind),4,nx)
qf=matrix(q(ind),4,nx)
endfunction
function [Xm,Xp,Ym,Yp,Zm,Zp] = slice_parallelepiped(dir, val, ebox, nx, ny, nz)
//
// ebox = [xmin xmax ymin ymax zmin zmax]
// dir : string "x=", val
// n1 et n2 les discretisations
//
coef = 5.e-3;
select dir
case "x=" then
if val < ebox(1) | ebox(2) < val then
error("bad slice choosen")
end
dx = coef*(ebox(2)-ebox(1))
y = linspace(ebox(3),ebox(4),ny)
z = linspace(ebox(5),ebox(6),nz)
[Zm,Ym] = ndgrid(z,y)
Xm = (val-dx)*ones(Ym);
[Yp,Zp] = ndgrid(y,z)
Xp = (val+dx)*ones(Yp);
case "y=" then
if val < ebox(3) | ebox(4) < val then
error("bad slice choosen")
end
dy = coef*(ebox(4)-ebox(3))
x = linspace(ebox(1),ebox(2),nx)
z = linspace(ebox(5),ebox(6),nz)
[Xm,Zm] = ndgrid(x,z)
Ym = (val-dy)*ones(Xm);
[Zp,Xp] = ndgrid(z,x)
Yp = (val+dy)*ones(Xp);
case "z=" then
if val < ebox(5) | ebox(6) < val then
error("bad slice choosen")
end
dz = coef*(ebox(6)-ebox(5))
x = linspace(ebox(1),ebox(2),nx)
y = linspace(ebox(3),ebox(4),ny)
[Ym,Xm] = ndgrid(y,x)
Zm = (val-dz)*ones(Xm);
[Xp,Yp] = ndgrid(x,y)
Zp = (val+dz)*ones(Xp);
else
error("bad arg dir")
end // select
endfunction
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