Resources Documentation RenderMan :Users' Guide :RIS :Rendering :Outputs :

Arbitrary Output Variables

Arbitrary Output Variables (AOVs) are the secondary images produced by the renderer. There can be any number of them generated simultaneously and each one may go to a different file, a different display driver, or use different pixel filter settings. In some cases, special pixel filter modes may be used to avoid mixing values from different samples in a non-sensical way; typically these select a single sample to be representative of the whole pixel.

Broadly speaking, AOVs in RIS fall into three main categories: Built-in AOVs, Integrator (Global) AOVs, Custom AOVs, and Light Path Expressions.

Built-in AOVs

The built-in AOVs display mostly geometric information pertaining to points on the visible surfaces seen by the camera. These values are automatically generated by the renderer and are available as AOVs regardless of the active integrator. Here is the current list of available builtin-ins:

`point P` Position of the point hit by the incident ray
`float PRadius` Cross-sectional size of the ray at the hit point (Note: the exposure of the image at right has been multiplied for the purposes of this illustration.)
`float cpuTime` The time taken to render a pixel.
`float sampleCount` The number of samples taken for the resulting pixel. (Note: the exposure of the image at right has been reduced since samples begin at value 1.)
`normal Nn` Normalized shading normal
`normal Ngn` Normalized geometric normal (Note: in this particular example, the shading and geometric normals are the same.)
`vector Tn` Normalized shading tangent
`vector Vn` Normalized view vector (reverse of ray direction)
`float VLen` Distance to hit point along the ray
`float curvature` Local surface curvature
`float incidentRaySpread` Rate of spread of incident ray
`float mpSize` Size of the micropolygon that the ray hit
`float u`, `float v`, `float w` The parametric coordinates on the primitive	u
`float du`, `float dv`, `float dw` Derivatives of u, v, and w to adjacent micropolygons	du
`vector dPdu`, `vector dPdv`, `vector dPdw` Direction of maximal change in u, v, and w	dPdu
`float dufp`, `float dvfp`, `float dwfp` Multiplier to dPdu, dPdv, dPdw for ray differentials	dufp
`float time` Time sample of the ray
`vector dPdtime` Motion vector
`float id` Returns the integer assigned via the identifier attribute as the pixel value (Note: the exposure has been reduced in the image at right for the purpose of illustration.)
`float outsideIOR` Index of refraction outside this surface

Integrator (Global) AOVs

On top of regular LPE-based AOVs, this integrator ouptuts a number of standard AOVs typically used by compositors.

Declaration	Contents	Channels
`color __Pworld`	P in world-space	`__Pworld.r` : x component `__Pworld.g` : y component `__Pworld.b` : z component
`color __Nworld`	Nn in world-space	`__Nworld.r` : x component `__Nworld.g` : y component `__Nworld.b` : z component
`color __depth`	Multi-purpose AOV	`__depth.r` : depth from camera in world-space `__depth.g` : height in world-space `__depth.b` : geometric facing ratio : abs(Nn.V)
`color __st`	Texture coords	`__st.x` : s `__st.y` : t `__st.z` : 0.0
`color __Pref`	Reference Position primvar (if available)	`__Pref.r` : x component `__Pref.g` : y component `__Pref.b` : z component
`color __Nref`	Reference Normal primvar (if available)	`__Nref.r` : x component `__Nref.g` : y component `__Nref.b` : z component
`color __WPref`	Reference World Position primvar (if available)	`__WPref.r` : x component `__WPref.g` : y component `__WPref.b` : z component
`color __WNref`	Reference World Normal primvar (if available)	`__WNref.r` : x component `__WNref.g` : y component `__WNref.b` : z component

Custom AOVs

In addition to the above, some custom shading plugins may recognize other requests for AOVs and respond to them in their own particular ways. The names of these AOVs and what exactly gets displayed is up to the particular plugin.

Examples

A Tale of Three Dinos - We've played with the Dino example a bit here to show off some of the AOV support in PRMan's RIS mode. Note that, at this time, this particular .rib file is not included with the other examples.