// Scale and bias for the current precomputed table - the constant use here are the one that have been use when the table in LtcData.DisneyDiffuse.cs and LtcData.GGX.cs was use
// TODO: This is the max value allowed for emissive (bad name - but keep for now to retrieve it) (It is 8^2.2 (gamma) and 8 is the limit of punctual light slider...), comme from UnityCg.cginc. Fix it!
// Ask Jesper if this can be change for HDRenderPipeline
// TODO: This is the max value allowed for emissive (bad name - but keep for now to retrieve it) (It is 8^2.2 (gamma) and 8 is the limit of punctual light slider...), comme from UnityCg.cginc. Fix it!
// Ask Jesper if this can be change for HDRenderPipeline
#define EMISSIVE_RGBM_SCALE 97.0
// RGBM stuff is temporary. For now baked lightmap are in RGBM and the RGBM range for lightmaps is specific so we can't use the generic method.
// In the end baked lightmaps are going to be BC6H so the code will be the same as dynamic lightmaps.
// Same goes for emissive packed as an input for Enlighten with another hard coded multiplier.
// TODO: This function is used with the LightTransport pass to encode lightmap or emissive
float m = PerceptualRoughnessToRoughness(perceptualRoughness); // m is the real roughness parameter
float n = (2.0 / max(FLT_EPSILON, m*m)) - 2.0; // remap to spec power. See eq. 21 in --> https://dl.dropboxusercontent.com/u/55891920/papers/mm_brdf.pdf
n /= 4.0; // remap from n_dot_h formulatino to n_dot_r. See section "Pre-convolved Cube Maps vs Path Tracers" --> https://s3.amazonaws.com/docs.knaldtech.com/knald/1.0.0/lys_power_drops.html
// Performs a *non-linear* remapping which improves the perceptual roughness distribution
// and adds reflection (contact) hardening. The *accurate* version.
float m = PerceptualRoughnessToRoughness(perceptualRoughness);
perceptualRoughness = pow(2.0 / (n + 2.0), 0.25); // remap back to square root of real roughness (0.25 include both the sqrt root of the conversion and sqrt for going from roughness to perceptualRoughness)
#else
// MM: came up with a surprisingly close approximation to what the #if 0'ed out code above does.
// Remap to spec power. See eq. 21 in --> https://dl.dropboxusercontent.com/u/55891920/papers/mm_brdf.pdf
float n = (2.0 / max(FLT_EPSILON, m * m)) - 2.0;
// Remap from n_dot_h formulation to n_dot_r. See section "Pre-convolved Cube Maps vs Path Tracers" --> https://s3.amazonaws.com/docs.knaldtech.com/knald/1.0.0/lys_power_drops.html
n /= (4.0 * max(NdotR, FLT_EPSILON));
// remap back to square root of real roughness (0.25 include both the sqrt root of the conversion and sqrt for going from roughness to perceptualRoughness)
perceptualRoughness = pow(2.0 / (n + 2.0), 0.25);
// Performs *linear* remapping for runtime EnvMap filtering.
// Ref: See "Moving Frostbite to PBR" Listing 22
// This formulation is for GGX only (with smith joint visibility or regular)
float3 GetSpecularDominantDir(float3 N, float3 R, float roughness)
{
float a = 1.0 - roughness;
float lerpFactor = a * (sqrt(a) + roughness);
// The result is not normalized as we fetch in a cubemap
sebastienlagarde
8 年前