








                        The RADIANCE
                  Synthetic Imaging System


                         Greg Ward
                Lawrence Berkeley Laboratory
                      1 Cyclotron Rd.
                    Berkeley, CA  94720
                       (415) 486-4757






1.  Introduction

     RADIANCE was developed as a research tool for  predict-
ing  the  distribution  of  visible radiation in illuminated
spaces.  It takes as  input  a  three-dimensional  geometric
model  of  the  physical  environment, and produces a map of
spectral radiance values as a color image.  The technique of
ray-tracing  follows light backwards from the image plane to
the source(s).  Because it can produce realistic images from
a  simple description, RADIANCE has a wide range of applica-
tions in  graphics  arts,  lighting  design,  computer-aided
engineering and architecture.

     The diagram in Figure 1 shows the flow between programs
(boxes)  and  data  (ovals).   The central program is rpict,
which produces a picture from a scene description.  Rview is
a  variation  of  rpict  that  computes  and displays images
interactively.

     A scene description file lists the surfaces and materi-
als  that  make up a specific environment.  The current sur-
face types are  spheres,  polygons,  cones,  and  cylinders.
They  can be made from materials such as plastic, metal, and
glass.  Light sources can be distant disks as well as  local
spheres and polygons.

     From a three-dimensional scene description and a speci-
fied  view,  rpict produces a two-dimensional image.  A pic-
ture file is a compressed binary representation of the  pix-
els  in  the  image.  This picture can be scaled in size and
brightness, anti-aliased, and sent to a graphics output dev-
ice.

     A header in each picture file lists the program(s)  and
parameters that produced it.  This is useful for identifying
a picture without having to display it.  The information can







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