Softimage SDK Programmer's Guide > Working with the SDK > Animation > Expressions >

# Creating Expressions

Expressions can be created using scripting commands, the Parameter.AddExpression or Parameter::AddExpression method. The SetExpr command substitutes an Expression or Expression object for the specified parameter's value by using an expression function (see Expression Reference for more information on available expression functions).

Tip

The AddExpr command basically does the same thing as the SetExpr command, but it also displays the new expression in the Expression Editor.

## Python Example: Setting an Expression with the SetExpr Command

This is the above example written in Python:

    from win32com.client import constants as c
    n = Application.ActiveSceneRoot.AddNull( "Null4Expr" )
    params = n.posx.FullName+","+n.posy.FullName+","+n.posz.FullName
    Application.SetExpr( params, "RAND(17,2,7)" )

Note

The thread of this example continues with accessing the expression in Python Example: Using the GetSource Command, in which the siSourceType enum is used (which is why the constants module was imported).

## JScript Example: Setting an Expression with the Parameter.AddExpression Method

Applying the random expression produces a kind of a buzzing effect:

    var n = Application.ActiveSceneRoot.AddNull( "Null4Expr" );
    n.posx.AddExpression( "RAND(17,2,7)" );
    n.posy.AddExpression( "RAND(17,2,7)" );
    n.posz.AddExpression( "RAND(17,2,7)" );

Note

The thread of this example continues with accessing the expression in JScript Example: Using the Source Property.

## C++ API Example: Setting an Expression with the Parameter::AddExpression Member Function

The following snippet is the C++ API equivalent of the previous JScript example:

    // Setup
    Application app = Application();
    Model root = app.GetActiveSceneRoot();
    Null n; root.AddNull( L"Null4Expr", n );

    // Get Parameters for names
    Parameter posx = n.GetParameter(L"posx");
    Parameter posy = n.GetParameter(L"posy");
    Parameter posz = n.GetParameter(L"posz");

    // Set the expression
    posx.AddExpression( L"RAND(17,2,7)" );
    posy.AddExpression( L"RAND(17,2,7)" );
    posz.AddExpression( L"RAND(17,2,7)" );

Note

The thread of this example continues with accessing the expression in C++ Example: Using the GetSource Member.