The MTV raytracer was written by Mark Terrence VandeWettering. The image format, if it can be called that, simply consists of an ascii single line header giving the width and height of the image followed by the binary data as r,g,b triples (one unsigned byte each). This is also the format supported RayShade, a volume rendering package by Craig Kolb.An extract from the MTV readme.....
The output from the raytracer is very simple, and not directly tied to any specific device. It consists of a single line, with format in C scanf style of "%d %d\n", which gives the resolution of the image. It is then followed by x*y sets of (red green blue) bytes.