The RenderMan Interface - Paul Bourke

Section 1
INTRODUCTION
The RenderMan Interface is a standard interface between modeling programs and rendering
programs capable of producing photorealistic quality images. A rendering program
implementing the RenderMan Interface differs from an implementation of earlier graphics
standards in that:
• A photorealistic rendering program must simulate a real camera and its many attributes
besides just position and direction of view. High quality implies that the
simulation does not introduce artifacts from the computational process. Expressed
in the terminology of computer graphics, this means that a photorealistic rendering
program must be capable of:
– hidden surface removal so that only visible objects appear in the computed image,
– spatial filtering so that aliasing artifacts are not present,
– dithering so that quantization artifacts are not noticeable,
– temporal filtering so that the opening and closing of the shutter causes moving
objects to be blurred,
– and depth of field so that only objects at the current focal distance are sharply in
focus.
• A photorealistic rendering program must also accept curved geometric primitives
so that not only can geometry be accurately displayed, but also so that the basic
shapes are rich enough to include the diversity of man-made and natural objects.
This requires patches, quadrics, and representations of solids, as well as the ability to
deal with complicated scenes containing on the order of 10,000 to 1,000,000 geometric
primitives.
• A photorealistic rendering program must be capable of simulating the optical properties
of different materials and light sources. This includes surface shading models
that describe how light interacts with a surface made of a given material, volume
shading models that describe how light is scattered as it traverses a region in space,
and light source models that describe the color and intensity of light emitted in different
directions. Achieving greater realism often requires that the surface properties
of an object vary. These properties are often controlled by texture mapping an image
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