Method eval

src/testrender/shading.cpp:104–107

struct Diffuse : public BSDF, DiffuseParams {
    Diffuse(const DiffuseParams& params) : BSDF(), DiffuseParams(params) { if (trans) N = -N; }
    virtual float eval  (const OSL::ShaderGlobals& sg, const OSL::Vec3& wi, float& pdf) const {
        pdf = std::max(N.dot(wi), 0.0f) * float(M_1_PI);
        return 1.0f;
    }
    virtual float sample(const OSL::ShaderGlobals& sg, float rx, float ry, float rz, OSL::Dual2<OSL::Vec3>& wi, float& pdf) const {
        Vec3 out_dir;
        Sampling::sample_cosine_hemisphere(N, rx, ry, out_dir, pdf);