Define how the object's centers should be distributed throughout the domain. The Center, for short and curved fibers (not for infinite), can be set to distribute Uniformly, On Current Objects (whenCreate in Current Domainis checked under Create Options), Uniformly in Box, or to follow a Density Distribution. The position of short and curved fibers in a generated structure can be controlled by adjusting the position of their Center through the Edit… button. In the image below the Center dialog is shown for Create in Current Domain unchecked (left) and checked (right).
When Uniformly Distributed is checked, the random fiber center values are uniformly distributed across the whole structure. The uniform distribution of the centers is clearly observed when the fibers in the structure are fairly short circular fibers.
The option to position the centers On Current Objects appears in the Center dialog only when Create in Current Domain is checked under the Create Options tab.
Observe the placement of short circular fibers’ centers on the loaded cone structure (generated with GadGeo), when On Current Objects is chosen in the Center dialog.
With Uniformly in Bounding Box checked, the values entered for X‑min, X‑max, Y-min, Y‑max, Z‑min and Z‑max, limit the distribution of the center’s positions to certain areas.
These values define an area in which the fiber centers are placed. For a 200 x 200 x 200 µm structure, the values in the dialog limit an area in which the fibers’ centers lay between 20 µm and 100 µm in the X-direction, 30 µm and 100 µm in the Y-direction, and between the origin (0 µm) and the end of the domain in the Z-direction.
The Density Distribution table describes the probability of a random center taking certain position values in Z-direction.
Important! The center density distribution must be defined with monotonously increasing z-values. If z is non-monotonic or monotonously decreasing, an error message appears when trying to generate the structure.
When checking Use Relative Position, in the density distribution table, the left column values from 0 to 1 correspond to locations in the structure. In the Z-direction, the value 0 is at the origin and the value 1 is at end of the domain. The right column assigns relative density values at these locations. The value 10 means that there are five times more fiber centers at Z = 1 than at Z = 0.1, with a density value of 2. The fiber density increases and decreases linearly between the given locations in the Z-direction.
With Use Relative Position unchecked, the left column values of the density distribution table correspond to absolute locations in the structure. The position values are coordinates to be entered in the given unit. Thus, to define the positions consider origin and periodicty. If Origin Z is set to 0, the value 0 lays in the origin. If Origin Z is set to 50, position 0 lays 50 µm outside of the domain or,if Periodic Z is checked additionally, 50 µm before the domain's end in Z-direction.
The right column assigns density values at these locations, where 0 means that fiber centers are absent at that location, and values larger than 0 means that fiber centers are present at the location.
In a structure of size 200 x 200 x 200 µm3 and origin set to (0,0,0), .observe how, with the values in these tables, fibers are absent or appear at the given locations. The fiber density increases and decreases linearly between the given locations in the Z-direction.
The same structures can be obtained when using or not using relative positions, as seen in the following example. Both structures are based on the same random seed.
As before with orientation, the distribution of centers can be separately set for each fiber type so that differently distributed fiber types may coexist within the same structure. In the following structures, observe that the gray short circular fibers are distributed Uniformly in Box, whereas the red short circular fibers follow a Density Distribution.
