I want design a new shading model to hair,but I don’t know how to get UV and Texture in Shadingmodel.ush.
this is shadermodel .et: https://www.cs.drexel.edu/~david/Classes/CS586/Papers/p271-kajiya.pdf
this is my shading model code.
float3 ShiftTangent(half3 T, half3 N, half shift)
{
float3 shiftedT = T + (shift * N);
return normalize(shiftedT);
}
float StrandSpecular(half3 T, half3 V, half3 L, half3 exponent)
{
float3 H = normalize(L + V);
float dotTH = dot(T, H);
float sinTH = sqrt(1.0 - dotTH * dotTH);
float dirAtten = smoothstep(-1.0, 0.0, dot(T, H));
return dirAtten * pow(sinTH, exponent);
}
//FMaterialPixelParameters MaterialParameters,
FDirectLighting HairShaderBxDF(FGBufferData GBuffer, half3 N, half3 V, half3 L, float Falloff, float NoL, FAreaLight AreaLight, FShadowTerms Shadow)
{
float3 tangent = cross(N, V);
// shift tangents
float2 UV = 1;
float shiftTex = tex2D(, )-0.5;
float3 t1 = ShiftTangent(tangent, N, 0.01 + shiftTex);
float3 t2 = ShiftTangent(tangent, N, 0.05 + shiftTex);
// diffuse lighting
float3 diffuse = saturate(lerp(0.25, 1.0, dot(N, V)));
// specular lighting
float3 specularColor1 = { 0.9, 0.9, 0.9 };
float3 specular = specularColor1 * StrandSpecular(t1, V, L, 1000);
// add second specular term
float specMask = tex2D(, UV);
float3 specularColor2 = { 0.68, 0.68, 0.68 };
specular += specularColor2 * specMask * StrandSpecular(t2, V, L, 100);
// Final color
FDirectLighting Lighting;
const float3 BsdfValue = HairShading(GBuffer, L, V, N, Shadow.TransmissionShadow, Shadow.HairTransmittance, 1, 0, uint2(0, 0));
Lighting.Diffuse = diffuse;
Lighting.Specular = specular;
Lighting.Transmission = AreaLight.FalloffColor * Falloff * BsdfValue;
return Lighting;
}