RealFlow's “Fracture” toolset consists of four individual applications:

Voronoi Uniform
Voronoi By Steering Geometry
Voronoi By Points
Voronoi Radial

The "Voronoi Tools" icons.

With these four modes you have almost endless possibilities for creating debris parts, broken glass, splinters and all kinds of fragments. Fragments became essential for many VFX shots, and RealFlow's capability to combine fluids with rigid or soft bodies opens a whole new world of realistic simulations.

With our “Fracture” toolset you can cover almost any fragmentation tasks directly inside RealFlow without having to use an external solution or transfer the pieces from your 3D software to RealFlow. Another advantage is that our tool only creates a single object – a so-called “MultiBody”. This means that you do not have to deal with hundreds or even thousands of nodes. Even the objects’ rigid or soft body parameters are managed within just one panel, but all settings will affect the individual pieces grouped in the “MultiBody”. Of course, “MultiBodies” are supported by RealFlow's exchange. There you simply load the appropriate SD file and import the data. The plugin recreates the individual fragments and adds them to your 3D software, where you can add textures. Alternatively you can save the fragments as Alembic files.

If you want to know the MultiBody’s actual number of pieces, please take a look at the object’s viewport information at the upper left corner (the screen caption) or go to:

File > Summary Info

The fragmentation process itself is very easy to control and even with the tool's default settings you are able to create stunning results on the fly. It just requires a few steps:

Add and select the object(s) you intened to fragment.
Optional: create a helper object, e.g. a “Null” or any other geometry from the tool's advanced fragmentation modes.
Launch the desired “Fracture” tool from the icon bar or with “Tools > Fracture …”.
Chose your settings, or leave the default parameters, and click “OK”.

Please note that this process is non-destructive and the original objects are retained. Another thing you should bear in mind is that only one MultiBody will be considered: no matter how many MultiBodies you select, the fragmentation will only be applied on the first MultiBody. Individual nodes, e.g. from SD or ABC files, are not restricted and you can use multi-selections as well.

Voronoi Fragmentation

To get a better idea of how these modes work, it is important to understand the principle behind the fragmentation process:

For the fragmentation of objects in 3D the so-called Voronoi method is used. Since this is a rather complex procedure we will give a brief overview for the 2D case. In the first step, points are scattered over a given area. These points are called seeds and they can be randomly distributed or follow a pattern – this is up to you. The fragments are then created around these seeds and the distance between these Voronoi centres influences the shape of the cells. A cell is a region that is closer to its corresponding seed than to any other seed.

In other words, the distribution of the initial points is responsible for the cell's shape and size. This way it is possible to create regions with a higher density of fragments just by spreading more points along a line, inside or outside of a reference shape or within a certain distance from an object and so on.

The “Apply globally” Option

Some “Fracture” tools provide an option called “Apply globally”. Since you can achieve very nice effects with it, we have collected some more information for you.

“Apply globally” can only be applied on a (single) MultiBody. Normally, the Voronoi pattern is created for each object individually, but this is not always wanted: Imagine an object that hits a floor consisting of individual tiles. The object creates a crack that spreads all over the floor. Without this option, you will not be able to create a propagating crack, because each tile will have a completely different pattern applied. In order to achieve a continuous crack, “Apply globally” has to be active, because in this case the object selection will be treated as one object and the fragmentation pattern is “spread” globally over the entire floor.

A very nice field of application is the creation of splinters. Currently, RealFlow's “Fracture” tools do not provide a dedicated mode for this fragmentation type, but there is an easy way to achieve this pattern. This method works best when all nodes share the same orientation, while size can vary:

Create your construction inside your 3D program
Import it as a MultiBody
Shorten it along one axis (ideally this is the orientation of the splinters)
Apply the fragmentation with “Apply globally”
Enlarge the new MultiBody to the original size of the reference object

Splinters, created with the method described above and rendered with RealFlow's Maxwell Render engine.

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