Graphics Reference
In-Depth Information
float dbv0 = -3. * (1.-v) * (1.-v);
float dbv1 = 3. * (1.-v) * (1.-3.*v);
float dbv2 = 3. * v * (2.-3.*v);
float dbv3 = 3. * v * v;
// finally we get to compute something
gl_Position =
bu0 * ( bv0*p00 + bv1*p01 + bv2*p02 + bv3*p03 )
+ bu1 * ( bv0*p10 + bv1*p11 + bv2*p12 + bv3*p13 )
+ bu2 * ( bv0*p20 + bv1*p21 + bv2*p22 + bv3*p23 )
+ bu3 * ( bv0*p30 + bv1*p31 + bv2*p32 + bv3*p33 );
vec4 dpdu =
dbu0 * ( bv0*p00 + bv1*p01 + bv2*p02 + bv3*p03 )
+ dbu1 * ( bv0*p10 + bv1*p11 + bv2*p12 + bv3*p13 )
+ dbu2 * ( bv0*p20 + bv1*p21 + bv2*p22 + bv3*p23 )
+ dbu3 * ( bv0*p30 + bv1*p31 + bv2*p32 + bv3*p33 );
vec4 dpdv =
bu0 * ( dbv0*p00 + dbv1*p01 + dbv2*p02 + dbv3*p03 )
+ bu1 * ( dbv0*p10 + dbv1*p11 + dbv2*p12 + dbv3*p13 )
+ bu2 * ( dbv0*p20 + dbv1*p21 + dbv2*p22 + dbv3*p23 )
+ bu3 * ( dbv0*p30 + dbv1*p31 + dbv2*p32 + dbv3*p33 );
teNormal = normalize( cross( dpdu.xyz, dpdv.xyz ) );
}
Figure 13.12.
The shader output for different outer and inner tessellation levels: outer = inner = 5 (left); outer
= 10, inner = 5 (middle); outer = inner = 10 (right).
