Aqsis 1.2 and above implements all the required features of the RenderMan Interface Specification:
It is worth mentioning that Aqsis allows //all// shader types, including [[[doc:imagershaders|imager shaders]] to be written in SL, a feature that is still unsupported by most commercial renderers, including Pixar’s PRMan.
The set of required features in the specification is actually rather small, and Aqsis, like most other RenderMan-compliant renderers, also supports many additional features. The specification lists the following optional advanced capabilities. Some of them are implemented by Aqsis, and some are being considered.
Aqsis supports a number of additional advanced features that are not mentioned in the RenderMan Interface specification. Most of these features are modeled after other renderers. This section provides overviews of the additional features in the style of the RISpec.
FIXME - write detailed specification (modelled on the RISpec) for each of the interface extensions.
The ambient occlusion at a point on a surface is the amount of light which can reach that point directly from infinity. This provides a cheap kind of approximate global illumination - deep holes in a surface are dark and edges are highligthed when lit with an ambient occlusion light source.
The ambient occlusion may be computed by tracing rays in all directions from the point and finding which ones go to infinity, or by rendering depth maps from multiple points of view. Conceptually, the depth map approach is equivilant to having multiple ambient shadow lights lighting the scene from many directions, and is the method supported by Aqsis.
For a tutorial-style guide to using ambient occlusion, see [[guide:ao|Ambient occlusion]].
RtVoid RiMakeOcclusion ( RtInt npics, RtString picfiles, RtString shadowfile, ...parameterlist... )
Create an ambient occlusion map from npics depth files stored in the array picfiles. The depth files should result from rendering the scene from multiple viewpoints. Depending on scene setup, such viewpoints are typically spaced evenly over a sphere or hemisphere centred on the object to be lit.
MakeOcclusion picfiles shadowfile ...parameterlist...
The number of input files is defined implicitly by the length of the picfiles array.
MakeOcclusion ["ao1.z" "ao2.z" "ao3.z" "ao4.z"] "ambient.map"
The RenderMan interface defines a procedure RiGeometry for the purpose of implementation specific geometry types. Aqsis uses this interface to provide simple access to some of the more common geometry types familiar to the computer graphics community.
RtVoid Rieometry ( RtToken type, ...parameterlist... )
This procedure provides a way for implementations to provide custom geometry types. Aqsis provides the following additional types.
Geometry type ...parameterlist...
RiGeometry ( "teapot", RI_NULL ); RiGeometry ( "bunny", RI_NULL );
FIXME: document the following interface extensions -
RtVoid RiIfBegin ( RtString condition ) RtVoid RiElseIf ( RtString condition ) RtVoid RiElse() RtVoid RiIfEnd()
RiShaderLayer ( RtToken type, RtToken name, RtToken layername, ...parameterlist... ) RiConnectShaderLayers ( RtToken type, RtToken layer1, RtToken variable1, RtToken layer2, RtToken variable2 )
RiMitchellFilter RiDiskFilter RiBesselFilter