光照方程中的高光部分
',5)),Q("mjx-container",p,[(t(),a("svg",H,T[0]||(T[0]=[m('// make the simplyfying assumption that V equals R equals the normal
vec3 R = N;
vec3 V = R;
const uint SAMPLE_COUNT = 1024u;
vec3 prefilteredColor = vec3_splat(0.0);
float totalWeight = 0.0;
for(uint i = 0u; i < SAMPLE_COUNT; ++i)
{
// generates a sample vector that's biased towards the preferred
//alignment direction (importance sampling).
vec2 Xi = Hammersley(i, SAMPLE_COUNT);
vec3 H = ImportanceSampleGGX(Xi, N, roughness);
vec3 L = normalize(2.0 * dot(V, H) * H - V);
float NdotL = max(dot(N, L), 0.0);
if(NdotL > 0.0)
{
prefilteredColor += texture2D(s_texSkybox, SampleSphericalMap(L)).rgb * NdotL;
totalWeight += NdotL;
}
}
prefilteredColor = prefilteredColor / totalWeight;
观察公式的第二个拆分项
`,3)),Q("mjx-container",Z1,[(t(),a("svg",x1,T[92]||(T[92]=[m('vec2 IntegrateBRDF(float NdotV, float roughness)
{
vec3 V;
V.x = sqrt(1.0 - NdotV*NdotV);
V.y = 0.0;
V.z = NdotV;
float A = 0.0;
float B = 0.0;
vec3 N = vec3(0.0, 0.0, 1.0);
const uint SAMPLE_COUNT = 1024u;
for(uint i = 0u; i < SAMPLE_COUNT; ++i)
{
// generates a sample vector that's biased towards the
// preferred alignment direction (importance sampling).
vec2 Xi = Hammersley(i, SAMPLE_COUNT);
vec3 H = ImportanceSampleGGX(Xi, N, roughness);
vec3 L = normalize(2.0 * dot(V, H) * H - V);
float NdotL = max(L.z, 0.0);
float NdotH = max(H.z, 0.0);
float VdotH = max(dot(V, H), 0.0);
if(NdotL > 0.0)
{
float G = GeometrySmith(N, V, L, roughness);
float G_Vis = (G * VdotH) / (NdotH * NdotV);
float Fc = pow(1.0 - VdotH, 5.0);
A += (1.0 - Fc) * G_Vis;
B += Fc * G_Vis;
}
}
A /= float(SAMPLE_COUNT);
B /= float(SAMPLE_COUNT);
return vec2(A, B);
}