G4RayTracer  version 1.0  (29/Jan/00)

1. Introduction

 G4RayTracer is a "ray tracing" package which uses Geant4 kernel mechanism
of tracking/navigation. It visualizes any kinds of solids that Geant4
kernel can navigate.

2. Building a library

 G4RayTracer is one of visualization driver which Geant4 supports. To build
a library of G4RayTracer (library name G4RayTracer), set an environment
variable G4VIS_BUILD_RAYTRACER_DRIVER.

 $ setenv G4VIS_BUILD_RAYTRACER_DRIVER 1

3. Using G4RayTracer

 To use G4RayTracer, set an environment variable G4VIS_USE_RAYTRACER.

 $ setenv G4VIS_USE_RAYTRACER 1

Also, G4RayTracer has to be registored to the user's concrete VisManager.
Refer an example given in 
  geant4/source/visualization/management/include/MyVisManager.cc.

4. Notes

a) G4RayTracer generates JPEG file(s). To visualize these files, use your
local program such as NetScape or xview, etc.

b) The eye position must be inside of the defined world volume. If you want 
to draw your detector setup from very far position, you need to enlarge
your world volume.

c) G4RayTracer ignores volumes without G4VisAttributes, volumes which are
set as "forced wire frame", and volumes which are set as "invisible".

d) In case you get unexpected figure, check 
 d.1) eye position and target position are properly set,
 d.2) light direction is properly set (note light direction is from
     illumination light source to the objects),
 d.3) span angle (given by angle for 100 pixels) is reasonable,
 d.4) there is no surrounding volume(s) without transparency.

e) G4RayTracer can be executed ONLY AT "Idle" state.

5. Basic UI commands

a) /vis/rayTracer/eyePosition x y z unit
    eye position

b) /vis/rayTracer/target x y z unit
    target position
    in default it is set to the origine

c) /vis/rayTracer/lightDirection ex ey ez
    vector of the illuminating light (need not to be a unit vector)
    note light direction is from illumination light source to the objects

d) /vis/rayTracer/column nColumn
    number of holizontal pixels
    in default 640 pixels

e) /vis/rayTracer/row nRow
    number of virtical pixels
    in default 640 pixels

f) /vis/rayTracer/span angle unit
    angle for 100 pixels
    in default 5 degree

g) /vis/rayTracer/trace fileName
    execution of G4RayTracer
    "fileName" is the out put JPEG file name 
    in default "g4RayTracer.jpeg"
    NOTE THAT THIS COMMAND IS AVAILABLE ONLY AT IDLE STATE