12.7 Parametric Subdivision 593
ysstt[0][0] = xsstt_0m;
ysstt[1][0] = xsstt_mm;
ysstt[0][1] = xsstt[0][1];
ysstt[1][1] = xsstt_m1;
Subdivide(s0,sm,tm,t1,y,yss,ytt,ysstt);
// subblock [sm,s1]x[t0,tm]
y[0][0] = x_m0;
y[1][0] = x[1][0];
y[0][1] = x_mm;
y[1][1] = x_1m;
yss[0][0] = xss_m0;
yss[1][0] = xss[1][0];
yss[0][1] = xss_mm;
yss[1][1] = xss_1m;
ytt[0][0] = xtt_m0;
ytt[1][0] = xtt[1][0];
ytt[0][1] = xtt_mm;
ytt[1][1] = xtt_1m;
ysstt[0][0] = xsstt_m0;
ysstt[1][0] = xsstt[1][0];
ysstt[0][1] = xsstt_mm;
ysstt[1][1] = xsstt_1m;
Subdivide(sm,s1,t0,tm,y,yss,ytt,ysstt);
// subblock [sm,s1]x[tm,t1]
y[0][0] = x_mm;
y[1][0] = x_1m;
y[0][1] = x_m1;
y[1][1] = x[1][1];
yss[0][0] = xss_mm;
yss[1][0] = xss_1m;
yss[0][1] = xss_m1;
yss[1][1] = xss[1][1];
ytt[0][0] = xtt_mm;
ytt[1][0] =