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. Color information about each individual triangle is included for all files unless in the brief mode. 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.