Behavior of Materials in RADIANCE

R( → P, v) Value of a ray starting at → P in direction v (in watts/sr/mˆ2) → Po Eye ray origin v Eye ray direction → Ps Intersection point of ray with surface n Unperturbed surface normal at intersection an Real argument number n C Material color, {a1, a2, a3} p Material pattern value, {1, 1, 1} if none → d Material texture vector, [0, 0, 0] if none → b Orientation vector given by the string arguments of anisotropic types n1 Index of refraction on eye ray side n2 Index of refraction on opposite side A Indirect irradiance (in watts/mˆ2) At Indirect irradiance from opposite side (in watts/mˆ2) m Mirror direction, which can vary with Monte Carlo sampling ts Specular threshold (set by -st option) Bi Radiance of light source sample i (in watts/sr/mˆ2) qi Direction to source sample i ω i Solid angle of source sample i (in sr)