XGen expression global variables

Floats

$aCount

The number of archive used by the current archive primitive.

$u

The u parameter of the underlying surface.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$v

The v parameter of the underlying surface.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$cLength

The final, computed length of the current primitive.

$cWidth

The final, computed width of the current primitive.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$cDepth

The final, computed depth of the current primitive without displacement.

$descId

The current description's ID.

$faceid

$faceId - The current face id.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$frame

The current frame being evaluated. This value should be used with care as it is not advisable for certain attributes to change across frames (for example, length and density) as this would make motion blur calculations impossible.

$id

The current primitive’s ID. This variable is useful for expressions involving modifiers.

$objectId

Alias for $patchId. Vectors.

$patchId

The current patch's ID.

Surface Vectors

$P

The surface point at which the primitive is being evaluated.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$Pg

The surface point without displacement.

$Pref

The reference surface point at which the primitive is being evaluated.

$Prefg

The reference surface point without displacement.

$Pw

The surface point at which the primitive is being evaluated. World space.

$Pgw

The surface point without displacement. World space.

$Prefw

The reference surface point at which the primitive is being evaluated. World space.

$Prefgw

The reference surface point without displacement. World space.

$dPdu

The surface dPdu at which the primitive is being evaluated.

$dPdug

The surface dPdu without displacement.

$dPduref

The reference surface dPdu at which the primitive is being evaluated.

$dPdurefg

The reference surface dPdu without displacement.

$dPdv

The surface dPdv at which the primitive is being evaluated.

$dPdvg

The surface dPdv without displacement.

$dPdvref

The reference surface dPdv at which the primitive is being evaluated.

$dPdvrefg

The reference surface dPdv.

Surface normal vectors

$N

The surface normal at which the primitive is being evaluated.

Note: Supported by Interactive Grooming Splines. See XGen Interactive Grooming.

$Ng

The surface normal without displacement.

$Nref

The reference surface normal at which the primitive is being evaluated.

$Nrefg

The reference surface normal without displacement.

Surface normal vectors

$N

The surface normal at which the primitive is being evaluated.

$Ng

The surface normal without displacement.

$Nref

The reference surface normal at which the primitive is being evaluated.

$Nrefg

The reference surface normal without displacement.

Image vectors and scalers

$Cs

Color surface for the current primitive.

$As

Alpha surface for the current primitive.

Important notes

• There are a set of variables describing underlying patch information that can be used in expressions. The vector forms may be used as vectors or individual components can be referenced. For example, $N refers to the surface normal vector, and $N[0] refers to the x component of the normal vector.
• Since the value of the displaced variables, such as for point (P) and normal (N) variables, depend on the displacement, offset and bump expressions values, those variables cannot be used within those expressions. If you wish to use point based noise, or any other expression that needs to use values from the underlying surface, you should use the g variety, such as Prefg and Nrefg.