// Initialization variables:
a = p+1;
b = a+1;
nb = 1;
c1 = 0;
c1 (nt+1) = 1;
mbar = p + 2 + nt + m;
ki = 1;
si = 1;
while b < mbar do
cnb+1 = 0; // Initialize the next extraction operator row.
// Count multiplicity of the knot at location b.
add = 0;
if si <= m && spans(si) = ki do
mult = 0;
add = 1;
// Add the new knot to the knot vector.
Ubar(b+1:mbar+p-m+si) = Ubar(b:mbar+p-m+si-1);
Ubar(b) = U(si);
si = si + 1;
else
ki = ki+1;
i = b;
while b < m && Ubar(b+1) == Ubar(b) do b = b+1;
mult = b-i+1;
end
if
mult < p do
numer = Ubar(b)-Ubar(a);
for j = p,p-1,. . .,mult+1 do
alphas(j-mult) = numer / (Ubar(a+j+add)-Ubar(a));
end
r = p-mult;
// Update the matrix coefficients for r new knots
for j=1,2,. . .,r do
save = r-j+1;
s = mult+j;
for k=p+1,p,. . .,s+1 do
alpha = alphas(k-s);
cnb (k) = alpha*cnb (k) + (1.0-alpha)*cnb (k-1);
end
if b < m do
// Update overlapping coefficients of the next operator row.
cnb+1 (save) = cnb (p+1);
end
end
nb = nb + 1; // Finished with the current operator.
if b < m
do
// Update indices for the next operator.
a = b;
Copyright ᭧ 2011 John Wiley & Sons, Ltd.
Int. J. Numer. Meth. Engng 2011; 88:126–156
DOI: 10.1002/nme
ISOGEOMETRIC FINITE ELEMENT DATA STRUCTURES FOR T-SPLINES
145
b = b+1;
end
end
end