4.12 Interfacing with Ray Tracing Programs
(Also see "Ray Tracing Output", "Brief", and "Output File Name" in "3D
Mode Selection" (p. 106).)
Fractint allows you to save your 3d transforms in files which may be fed
to a ray tracer (or to "Acrospin"). However, they are not ready to be
traced by themselves. For one thing, no light source is included. They
are actually meant to be included within other ray tracing files.
Since the intent is to produce an object which may be included in a
larger ray tracing scene, it is expected that all rotations, shifts, and
final scaling will be done by the ray tracer. Thus, in creating the
images, no facilities for rotations or shifting is provided. Scaling is
provided to achieve the correct aspect ratio.
WARNING! The files created using the RAY option can be huge. Setting
COARSE to 40 will result in over 2000 triangles. Each triangle can
utilize from 50 to 200 bytes each to describe, so your ray tracing files
can rapidly approach or exceed 1Meg. Make sure you have enough disk
space before you start.
Each file starts with a comment identifying the version of Fractint by
which it was created. The file ends with a comment giving the number of
triangles in the file.
The files consist of long strips of adjacent triangles. Triangles are
clockwise or counter clockwise depending on the target ray tracer.
Currently, MTV and Rayshade are the only ones which use counter
clockwise triangles. The size of the triangles is set by the COARSE
setting in the main 3d menu. Color information about each individual
triangle is included for all files unless in the brief mode.
To keep the poor ray tracer from working too hard, if WATERLINE is set
to a non zero value, no triangle which lies entirely at or below the
current setting of WATERLINE is written to the ray tracing file. These
may be replaced by a simple plane in the syntax of the ray tracer you
are using.
Fractint's coordinate system has the origin of the x-y plane at the
upper left hand corner of the screen, with positive x to the right and
positive y down. The ray tracing files have the origin of the x-y plane
moved to the center of the screen with positive x to the right and
positive y up. Increasing values of the color index are out of the
screen and in the +z direction. The color index 0 will be found in the
xy plane at z=-1.
When x- y- and zscale are set to 100, the surface created by the
triangles will fall within a box of +/- 1.0 in all 3 directions.
Changing scale will change the size and/or aspect ratio of the enclosed
object.
We will only describe the structure of the RAW format here. If you want
to understand any of the ray tracing file formats besides RAW, please
see your favorite ray tracer docs.
The RAW format simply consists of a series of clockwise triangles. If
BRIEF=yes, Each line is a vertex with coordinates x, y, and z. Each
triangle is separated by a couple of CR's from the next. If BRIEF=no,
the first line in each triangle description if the r,g,b value of the
triangle.
Setting BRIEF=yes produces shorter files with the color of each triangle
removed - all triangles will be the same color. These files are
otherwise identical to normal files but will run faster than the non
BRIEF files. Also, with BRIEF=yes, you may be able to get files with
more triangles to run than with BRIEF=no.
The DKB format is now obsolete. POV-Ray users should use the RAW output
and convert to POV-Ray using the POV Group's RAW2POV utility. POV-Ray
users can also do all 3D transformations within POV-Ray using height
fields.