The RenderMan Interface - Paul Bourke

An area light source is defined by a shader and a collection of geometric primitives. The association
between the shader and the geometric primitives is done by having the graphics
state maintain a single current area light source. Each time a primitive is defined it is added
to the list of primitives that define the current area light source. An area light source may be
turned on and off just like other light sources.
The RenderMan Interface includes four standard types of light sources: ”ambientlight”,
”pointlight”, ”distantlight”, and ”spotlight”. The definition of these light sources are given
in Appendix A, Standard RenderMan Interface Shaders. The parameters controlling these
light sources are given in Table 4.7, Standard Light Source Shader Parameters.
Light Source Parameter Type Default Description
ambientlight intensity float 1.0 Light intensity
lightcolor color color ”rgb” (1,1,1) Light color
distantlight intensity float 1.0 Light intensity
lightcolor color color ”rgb” (1,1,1) Light color
from point point ”shader” (0,0,0) Light position
to point point ”shader” (0,0,1) Light direction is fromto
pointlight intensity float 1.0 Light intensity
lightcolor color color ”rgb” (1,1,1) Light color
from point point ”shader” (0,0,0) Light position
spotlight intensity float 1.0 Light intensity
lightcolor color color ”rgb” (1,1,1) Light color
from point point ”shader” (0,0,0) Light position
to point point ”shader” (0,0,1) Light direction is fromto
coneangle float radians(30) Light cone angle
conedeltaangle float radians(5) Light soft edge angle
beamdistribution float 2.0 Light beam distribution
Table 4.7: Standard Light Source Shader Parameters
RtLightHandle RiLightSource ( RtToken shadername, ...parameterlist...)
shadername is the name of a light source shader. This procedure creates a non-area
light, turns it on, and adds it to the current light source list. An RtLightHandle value
is returned that can be used to turn the light off or on again.
RIB BINDING
LightSource name sequencenumber ...parameterlist...
The sequencenumber is a unique light identification number which is provided by
the RIB client to the RIB server. Both client and server maintain independent mappings
between the sequencenumber and their corresponding RtLightHandles. The
number must be in the range 0 to 65535.
EXAMPLE
42