Let us begin by looking at how exactly does Ornatrix take guides and represent them as real-world objects that can interact with the environment and all other objects.

Initially guides in the scene are nothing more than linked lists of linear segments. The number of segments and their shape are controlled by user and thus can be arbitrary. Ornatrix' modeling system's goal is to preserve the basic information about the structure of these segments so they can be accurately used by the dynamics engine for simulations.

Guides, however, are only virtual objects that control the shape of hundreds of thousands of real hairs. Not only does the dynamics engine have to convert these guides into real-world objects, but it also has to do so such that every guide represents a large clump of real hair.

This is done by converting every guide segment into a 3d volumetric shape. All of the dense hair associated with that particular segment is then presumed to be inside this volume and the volume simply represent the group of hairs inside it (with equal mass, shape, etc). The volume object that Ornatrix uses is a capsule. As you can see on the diagram to the right, capsules are created for every segment and every two consecutive capsules always intersect thus forming one continuous volume from root to tip.

From previous diagram you could also see that the capsules were too thin, thus representing the actual hair volume around them quite poorly. Ornatrix has an option ("Auto-size wisps") to automatically resize these capsules when simulation starts so that they take as much space as possible without penetrating at the root during first frame.

From the picture on the left you can see how this option resizes the capsules causing them to wrap the surrounding hairs better thus making more realistic simulation. One array of these capsules (representing a strand) is referred to as a wisp. Wisps are a very important part of dynamic simulation because they are the only way of representing many hair in a from that simulator understands.

Aside from allowing mutual collisions between wisps and objects, Ornatrix also provides an option that allows collisions of a wisp with itself. This means that two capsules located in the same wisps can potentially collide. Every two consecutive capsules are automatically prevented from colliding by the simulator because they will always inter-penetrate (due to the nature of wisp's structure).

On the diagram to your right you can see one exception that can occur when your capsule radius is too large, or you segments are too small. The capsules that are separated by a segment between them still penetrate. The segment between them forces these capsules to stick together and attracts them with great force. Because these two capsules penetrate, however, another great force pushes them apart. These two forces get accumulated by the amount of overall such collisions happening between capsules and can quickly de-stabilize your simulation.

The best technique to combat this is to know what kind of radius you need your wisps to be in order not to penetrate, or not to use wisp self-collision at all.

To your left you can see the above problem being solved by reducing the radii of the segment capsules, thus removing any penetration that occurred previously.

Because the actual wisps aren't hard objects by nature (hair is soft and energy absorbent), collisions between them shouldn't prevent them from penetrating completely. Rather it should allow for a soft penetration while still trying to push the two wisps apart.

Ornatrix achieves this by allowing 'soft' collisions between wisps. At the same time it uses hard collisions between wisps and external objects. These softness parameters are completely controllable from within dynamics simulation parameters.