Ray Casting and Rasterization - Computer Graphics: Principles and Practice - page 426

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const float w = -1.0f / T.vertex(v).z;
vertexW[v] = w;
vertexPw[v] = T.vertex(v) * w;
vertexNw[v] = T.normal(v) * w;

}

// For each pixel
for ( int y = y0; y < y1; ++y) {
for ( int x = x0; x < x1; ++x) {
// The pixel center
const Point2 Q(x + 0.5f, y + 0.5f);
...

}

}

}

}

Listing 15.28: Inner loop of a barycentric (edge align) rasterizer (see
Listing 15.27 for the loop setup).

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// For each pixel
for ( int y = y0; y < y1; ++y) {
for ( int x = x0; x < x1; ++x) {
// The pixel center
const Point2 Q(x + 0.5f, y + 0.5f);

// 2D Barycentric weights
const float weight2D[3] =
{bary2D(V[0], V[1], V[2], Q),
bary2D(V[1], V[2], V[0], Q),
bary2D(V[2], V[0], V[1], Q)};

if ((weight2D[0]>0) && (weight2D[1]>0) && (weight2D[2]>0)) {
// Interpolate depth
float w = 0.0f;
for ( int v = 0; v < 3; ++v) {
w += weight2D[v] * vertexW[v];

}

// Interpolate projective attributes, e.g., P', n'
Point3 Pw;
Vector3 nw;
for ( int v = 0; v < 3; ++v) {
Pw += weight2D[v] * vertexPw[v];
nw += weight2D[v] * vertexNw[v];

}

// Recover interpolated 3D attributes; e.g., P' -> P, n' -> n
const Point3 &P=Pw/w;
const Vector3 &n=nw/w;

const float depth = P.length();
// We could also use depth = z-axis distance: depth = -P.z

// Depth test
if (depth < depthBuffer.get(x, y)) {
// Shade
Radiance3 L_o;
const Vector3 & w_o = -P.direction();

// Make the surface normal have unit length
const Vector3 & unitN = n.direction();