GPU Pro 4

206 III Image Space

if ( edge_x)

{

float k0 = dx1 - dx0; // Left slope

float k1 = dx3 - dx2; // Right slope

float m0=dx1+k0;// Left offset

float m1 = dx2 - k1; // Right offset

offset .x = ( m1 - m0) / (k0 - k1); // Intersection point

is_silhouette = (abs(offset .x) > 1.0f );

offset .x = ( abs( offset .x) < 0.5f)? offset .x : 0.5f;

}

Listing 3.2. Computing horizontal crease intersection point.

In Listing 3.2 we are computing the intersection point horizontally. The math

is relatively straightforward, and the resulting value is the coordinate relative to

the center sample location. If the intersection point lands somewhere within a

pixel in either direction, ...