GLOBALS



ST

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These are the texture coordinates for the surface at P.

SSTT

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These are the texture coordinates for the surface at P,
which have been scaled and/or offset.

UV

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These are the parametric values of the surface at P.

UUVV

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These are the parametric values of the surface at P;
which have been scaled and/or offset.

DUDV

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These values are the rate of change in the surface at P.

TIME

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This is the shutter time.

DTIME

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This is the amount of time covered by this shading sample.

NCOMPS

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ncomps is the number of color components.
Default is 3: red green blue

P

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P is the position of the surface point.

N

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N is the shading normal of the surface point.
N = dPdu ^ dPdv

I

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I, the incidence vector, 
is where the camera vector intersects the surface point P.

L

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L is the vector from the light source to P.

DPDU

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dPdu is the rate of change of the surface with respect to u.

DPDV

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dPdv is the rate of change of the surface point with respect to v.

DPDTIME

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dPdtime is the vector indicating how the surface point P is 
changing over time, as indicated by motion blur in the scene. 
This is similar to how dPdu and dPdv give the rate of change 
in P over u and v, respectively. 

NG

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Ng is the geometric normal of the surface point.
Ng = dPdu ^ dPdv

E

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E is the camera postion.

PS

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Ps is the position of the surface point being shaded.

FROMRIBCOLOR

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The surface color which is set in the RIB stream.
The default is black.  Create a user defined color,
if you do not want that value used as the surface color.

FROMRIBOPACITY

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The surface opacity which is set in the RIB stream.
The default is white.  Create a user defined float 
if you do not want that value used as the surface opacity.

SURFACECOLOR

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This is the surface color returned to the Renderer.
It is the output of a Surface Shader.  The default is black.

SURFACEOPACITY

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This is the surface opacity returned to the Renderer.
It is the output of a Surface Shader.  The default is white.

LIGHTCOLOR

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This is the light color returned to the renderer.
It is the output of a Light Shader. The default is black.

LIGHTOPACITY

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This is the light opacity returned to the renderer.
It is the output of a Light Shader.  The default is white.

USERDEFINED

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This is a user defined constant of any data type.
The output and input should be of the same data type.

USERDEFINEDARRAY

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This is a user defined array of any data type.
All inputs should be of the same data type.
Please refer to the RenderMan Shading Language Extensions.

FRAMERANGE

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This box makes it easy to use start/end/current frame values 
from a rib file, returning a value between 0 and 1. 
0 returns when current frame is start frame, 1 when it's end frame.
If the current frame is outside the start/end frame, values will
fall outside of the 0 to 1 range. This is not recommended, but possible.

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