RIB Generators

RIB Generators provide a mechanism to import and manipulate procedural objects. Procedural objects are objects which are generated programatically through callbacks to the RenderMan interface. By attaching RIB Generators to coordinate systems and template objects in your scene you control the context in which your RIB Generators instantiate themselves.

RIB Generators are similar to shaders in that you can:

• write your own or obtain 3rd party plugins
• construct a .sli interface description
• import and manipulate them through the Slim Palette
• edit their parameters with the Appearance Editor

• written in C++, then compiled
• platform specific
• evaluated at rib generation time, not render time

• Using RIB Generators
• Writing RIB Generators

Using RIB Generators

Writing RIB Generators

The API for RIB Generators is quite simple. Every RIB Generator must:

• Create a subclass of the abstract RIBGen class. This class is defined in RIBGen.h. In your subclass you must implement the following methods:

  // Arguments from the UI are passed in as name/value pairs as
// in the RenderMan Interface. We assume that type information
// is known to the plugin.
virtual int SetArgs( int n, RtToken tokens[], RtPointer values[] );


  // Return a bounding box for your procedural geometry.
// This may be used to cull your geometry if it's offscreen.
virtual void Bound( RIBContext *, RtBound b );


  // Make calls through RenderMan Interface using information
// and entrypoints provided in the RIBContext object.
virtual int GenRIB( RIBContext * );


   

• Implement factory procedures for your subclass:

  extern "C" RIBGen  *RIBGenCreate();
  extern "C" void    RIBGenDestroy( RIBGen * );
  

• Use the RIBContext object to make calls to the RenderMan Interface or query the current RIB context. The RIBContext class is defined in: RIBContext.h. Query functions include:
  

  void        GetRenderingPass(RenderingPass *p, RtBoolean *declarePhase);
  RtBoolean   GetMotionBlur();
  void        GetMotionInfo( RtFloat *sa, RtFloat *FPS, RtBoolean *subframe );
  int         GetFrame();
  void        GetShutter(RtFloat *open, RtFloat *close);
  const char *GetObjName();
  void        GetCamBasis( RtMatrix m, int inverse = 0 );
  

• Write a .sli file describing the parameters to your RIBGen subclass. The .sli file is the authority when it comes to the number and datatypes of your arguments.

The best way to learn is always by example and  is a simple example of a custom RIB Generator. Example  files for ribgenDumpState can be found under $RATTREE/devkit/examples/ribgen.