ggx

Since	18.0

bsdf  ggx(vector ng, vector nn, vector xg, vector yg, vector F0, vector F90, float alphax, float alphay, int masking, int fresblend, float eta, float reflect, float refract, int reflectmask, int refractmask, float dispersion, ...)

Creates a BSDF for computation of the GGX microfacet model, used for rough specular reflection and refraction.

See writing a PBR shader for information on BSDFs.

ng

Normalized geometry normal

nn

Normalized bumped/shading normal

xg

Normalized x tangent vector

yg

Normalized y tangent vector

F0

Color tint at oblique angles

F90

Color tint at grazing angles

alphax

Roughness along the x tangent vector

alphay

Roughness along the y tangent vector (use the same value as alphax for isotropic)

masking

Enable/Disable microfacet masking

fresblend

0 = disable fresnel, 1 = enable fresnel, 2 = use critical angle to select between reflection and refraction.

eta

Index of refraction

reflect

Explicit scalar on reflection (0->1). Or -1 to let the function decide itself on the appriate value based on geometric information.

refract

Explicit scalar on refraction (0->1). Or -1 to let the function decide itself on the appriate value based on geometric information.

reflectmask

Bitmask representing the desired reflection behaviour. Simply passing in bouncemask(reflectlabel) will suffice

refractmask

Bitmask representing the desired refraction behaviour. Simply passing in bouncemask(refractlabel) will suffice

dispersion

Amount of dispersion

Light inclusion/exclusion options

light-inclusion-exclusion-options

“categories”, string ="*"

Specifies lights to include/exclude by their “category” tags. This is the preferred include/exclude lights rather than pattern matching light names with the "lightmask" keyword argument.

For example:

diff = diffuse(nml, "lightmask", "hero | fill");

See light categories for more information.

“lightmask”, string ="*"

When evaluating light and shadow shaders, objects have pre-defined light masks. This mask is usually specified in the geometry object and specifies a list of lights which are used to illuminate a surface or fog shader. It is possible to override the default light mask by specifying a “lightmask” argument.

For example:

diff = diffuse(nml, "lightmask", "light*,^light2");

…will cause all lights whose names begin with “light” except for a light named “light2” to be considered for diffuse illumination.

All Houdini scoping patterns, excepting group expansion, are supported:

• * - wild-card match
• ? - single character match
• ^ - exclusion operator
• [list] - character list match