This tool is perfectly suited for breaking glass or stucco, as well as objects hit by bullets or arrows. The control points that are used to rule the distribution of the fragments are positioned along concentric lines around a given centre. The result is a typical look similar to a spider web. Please take a look at the illustration below:

The squared background area represents the object that should be fragmented. The dark blue lines are the “rays”. Additionally, there is a light blue area called “annulus” – an area between two concentric circles. Inside the annulus you can see several white circles: in the tool's interface they are called “rings”.

Voronoi

In this section you find the basic settings for the creation of the Voronoi seeds.

Seed

If you want to avoid the same distribution of fragments, please enter a different random "Seed" value.

Apply globally

A global distribution of seeds is obligatory with this tool. For this reason, the checkbox cannot be accessed.

Reference system

This section provides everything you need to choose the reference node.

Source

Radial patterns are always created using a virtual focal point and a virtual 2D plane: as the image above shows, seeds are scattered on the plane around the focus point. The reference system of the source object (blue dot) determines the centre of the radial fragmentation and helps to determine which will be the spreading plane (with the selection of the "Front direction" axis below).

The reference object can be any node, even a daemon or emitter, although a “Null” object is certainly the best choice. Please note that the reference object can also be outside the node you want to break apart. You can enter either the exact name of an existing node in the input field, or choose one from a list that will be displayed with the “...” button.

Front direction

Here you can specify which axis should be used for determining the fragmentation’s plane (the centre has already been taken from the local system of the reference object). It is only possible to choose one axis and the radial pattern is created perpendicularly to the selected axis.

Rays

The rays can be considered the “connectors” of the rings: they are the lines from the centre of the chosen reference object pointing outwards. This section provides everything you need to control the rays.

Rays number

Here you can determine how many rays you want to create.

Ray angle randomness

By default, all rays are created with the same angle between them, but, in most cases, this uniform look is not intended. If you want to displace the rays you can enter a number between 0.0 and 1.0 (highest randomness).

Rings

A radial pattern consists of rays and concentric rings. To get an idea of the various inner and outer parameters, please take a look at this illustration and read the following introduction describing how the individual parameters work together:

The annulus is the area in which the rings are created and is defined through two parameters: “Annulus internal radius” (short, upper orange line) and “Annulus external radius” (long, lower red line).
The number of rings (white circles) is determined by the “Rings number inside annulus”.

When you take a look at a real object, e.g. a glass that has been hit by a stone, then you will observe that the number of rings decreases with growing distance from the annulus. Another effect is that the distance between these rings is growing with increasing distance from the annulus. You can see this in the illustration below. This effect can be controlled with “Internal transition length” (orange line) and “External transition length” (red line). Both values determine how far from the annulus, these extra rings are created. The distance between the rings outside the annulus is adjusted with “Internal transition decay” and “External transition decay”. To achieve a realistic radial fracture you normally only have to use the parameters of the “External” section, while the “Internal” panel is, in fact, only relevant for some special effects.

Left image: Rings without transition decay; right image: rings with transition decay.

Annulus internal radius

This is the inner radius of the annulus. The final size of the annulus’ area is defined by “Annulus internal radius” and its counterpart “Annulus external radius”.

Internal transition length

With this parameter you determine how far from the annulus’s internal radius additional rings are created. The length is given in metres.

Internal transition decay

Here you can define how fast the rings outside the annulus (measured from the inner boundary of the annulus) are separated. The value ranges between 0 (no decay) and 1 (maximum decay).

Annulus external radius

This is the outer radius of the annulus. The final size of the annulus’ area is defined by “Annulus external radius” and its counterpart “Annulus internal radius”.

External transition length

This parameter is used adjust how far from the annulus’s external radius additional rings are created. Again, this value is measured in metres.

External transition decay

Here you can define how fast the rings outside the annulus (measured from the outer boundary of the annulus) are separated. Valid values go from 0 (no decay) to 1 (maximum decay).

Rings number inside annulus

The annulus is the dense impact zone at the centre object. Pieces are created through the intersection of rays and rings. Simply enter the desired number of rings.

Rings radius randomness

By default, all rings inside the annulus are equispaced (they have exactly the same distance from each other; left image below), showing a uniform look. In transition zones, the rings obey the decay parameters – with a value of 0 (= no decay), the rings will be equispaced as well. To avoid this, enter a degree of randomness between 0.0 and 1.0 (maximum randomness).

Left image: rings without randomness are equispaced; right image: rings with randomness look more realistic.

Create central piece

When the checkbox is activated, the “Fracture” tool creates a fragment directly at the centre of the radial pattern.

Random

This is the place where you can apply a random or twisted look to the fragmentation pattern.

Noise

With this parameter you add a small amount of random displacement to the seed points to create a more random look. You can enter values between 0.0 and 1.0 (maximum noise)

Twist

You can also displace the seed points with a predefined radial pattern (this pattern is created internally). The amount of displacement is controlled with values between -1.0 (maximum twist counterclockwise) and 1.0 (maximum twist clockwise). The result is a typical look, similar to a spiral or the arrangement of sunflower seeds. With 0, no twist will be applied.

Channels

Split into internal/external (automatic criterion)

When you work with reference objects, the pieces are created in two zones with highest and lowest concentration of pieces. With this option it is possible to separate these fragments and store them in two individual “MultiBody” nodes.

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