Interfacing with Ray Tracing Programs

(Also see "Ray Tracing Output", "Brief", and "Output File Name" in a "3D Mode Selection" .)

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.

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This page maintained by

Noel Giffin,