Large scenes in any 3D render software require huge amounts of objects, which is most prominent in nature renders with grass and trees. Placing the objects by hand would cost more time than available in most productions, and therefore a technique has been developed many years ago known as instancing (or often called scattering). This technique repeats one and the same object across the scene, it scatters instances of the object across the scene, and each instance has a specific scale, position, rotation and so forth. All these properties are known as the transform of the respective instance.
A small scattering tool has been developed by Blue Budgie Studios, especially for use with Octane Render and nature scenes. Scattering the instances of the object is possible in Octane Render, but it is not able to produce the individual transforms for each instance. Instead, Octane Render takes csv files as input, where the user has to provide all the transforms. In math, the transforms are expressed as geometric transform matrices and one such matrix contains position, rotation, scale and shear of the instance. If 1000 trees are all bent, rotated and sheared and put in different positions in a scene, they will look like a natural forest. In a nutshell, what mScatter does for nature scenes is to take a terrain height map on which the user paints the grass population and so on, and then it produces the transform for each instance according to some randomizing algorithms. In the end, it outputs the csv file ready to be imported into Octane for creating fields and forests on the terrain.
Nature scenes are not the limit for mScatter and all possible kind of algorithms exist to create transforms for producing certain effects.
Octane Render requires standard transform matrices. A nice summary is here.
Another nice scattering tool for Octane Render, which even allows painting on objects, is available here for licensing.
It has evolved really nicely over the past years and is highly recommended. Even back when mScatter was coded, it could already cover a variety of applications, but unfortunately back in those days it was not able scatter grass, trees and so forth on terrains for landscape renders.