MLT is a path tracing process in which randomly distributed initial paths on the image surface are mutated according to special rules until all image pixels are covered and the desired accuracy and mutation rate are achieved.

The MLT raytracer in GroIMP is controlled via a separate parameter box in the raytracing options. The user has the option of selecting the mutation strategies to be used via checkboxes. They can also specify the number of initial paths in the <key>Count of seed paths</key> field. The most decisive parameter for the quality of the final image is the <key>Count of mutations per pixel</key> field, which determines the average target number of mutations per image pixel. It is important to note that the renderer tries to achieve this average value for all pixels of the image. For scenes that are mostly empty (e.g. an object floating freely in space without any surrounding elements), the pixels highlighted with an object are frequented correspondingly more frequently by the algorithm. As the bidirectional ray tracer is used in advance, its parameters also determine the length of the paths also determine those of the MLT raytracer.