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## 5.4. Parameters

The options in this submenu allow the user to specify certain parameters that act as variables for the geometry. This allows parametrizing our geometries in order to be able to run several simulations more easily by tuning the different parameters of the geometry (thus not being necessary to redo the geometry for different simulations).

This procedure works in the following way: the user defines several parameters and their value arrays (i.e. the possible values for the parameters) and assigns them to the geometry. This creates several states for the geometry, which we will call “steps”. A step is a geometry state in which each of the parameters takes the value of a specific index of its set of values. As an example, in step 1, every parameter takes the value of the first value of its value array; in step 2 the second value and so on. This means that there will be as many steps as the length of the larger value array of those parameters used in the geometry.

In this way, the user can use parameters while defining the geometry. For example, the following figure shows how to define a cube with a side length depending on a parameter called “myLength”.

Creating a parameterized cube

When using a parametrized geometry, the user will be able to view the results for each step in the options of the Show Results menu.

The options explained below will allow adding parameters and visualizing the effect of these parameters in the geometry view.

Options in the Parameters submenu

### 5.4.1. Define Parameters

After selecting this option, the following panel will be shown:

Define Parameters panel

In this panel the user can define the parameters needed to parametrize the geometry. In the figure above, we have defined a parameter with a value varying in the array of values (2.5, 5.0, 7.5, 10.0). The user can define new parameters with the Add parameter button, which will add a new row in the parameters table.

The name of the paramaters may satisfy the following requirements:

• Blank spaces are not allowed. For example, "new parameter" is not a valid name.
• No empty names are allowed.
• The name must be made-up only by alphanumeric characters and the "_" character. For example, both "parameter1", "parameter_1", "d" and "newParameter" are valid names, while both "new parameter", "parameter&1", "", and "?" are not valid names.

The user can set the array of values of each parameter manually. There are three ways to define parameters:

• Implicit linear values: with this way to parametrize the geometry, the user indicates the values of the parameter. The number of values introduced will define the number of steps that the objects parametrized obtain with this parameter. The syntax required for the implicit linear parameters definition is a list of values, separated with commas and surrounded between "{" and "}" characters, as in the below example.

{2, 5, 12.5, 15}

• Range of linear values: with this option, the program will assign a new array of values to the parameter. The values of this array will be uniformly chosen between the intervals, with as many values as the number introduced after the range.  The syntax required for the linear parameters definition is an interval defined by its initial and final values, separated with commas and surrounded between brackets, and followed by the number of samples (integer positive value) to be taken. See the following example to parametrize in this way:

[0.0,3.0] 4 The program will assign an array of values (0, 1, 2, 3)

• Values defined by functions: with this option, the user can specify an expression using other parameters and built-in functions. If the expression is a constant value (i.e. does not use parameters) the set of values generated for the parameter will be a singleton set containing that constant value. Otherwise, i.e. the function depends on previously defined parameters, the set of values will contain as many values as the smallest array used, and the actual values will be the result of the expression. See the following examples to parameterize in this way:

cos(90) Array of a singleton set.

sin(a) Array of different values using the "a" parameter created previously.

The auxiliary parameters are automatically defined when an operation is performed on an existing parameter, and their name starts always with the '\$' character to be identified. In this way, for example, given a parameter named 'Length', the using of 'Length/2.0' at any operation creates (or uses the previously created the following times) an auxiliary parameter named '\$x', where 'x' notation is an internal numeration.

The user can also delete existing parameters by selecting them and clicking the Delete parameter button.

Finally, the user may save the changes in the parameter list by pressing the Save button.

### 5.4.2. Set Step

This option allows the user to visualize an animation of the geometry as the value of each parameter cycles through the set of values of the parameter. When the user selects the Set Step option, the following panel will show:

Set Step panel

This panel allows the user to select a step to view on the geometry view. There are two available variation methods used to generate the steps:

• Cross join: Generates a step for every combinations of the possible values of the parameters used in the geometry. Parameters that are not used in the geometry will not be not considered.
• Linear: The values of the parameters are the values at a specific index (determined by the step) of the array of values. There will be as many steps as the maximum length of the value arrays of those parameters used in the geometry.

It is also possible, as mentioned before, to see an animation of the geometry view on each step. In order to do this, the user may change the time delay between steps and press the Run button.

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