WM Basic™ User's Manual - Classes

Chapter 1 Putting it All Together: A Simple WM Basic Program 37
Specifying Objects to be Controlled
To link WMInput to other objects in Working Model, you simply need to assign the input ID
to the desired property to be controlled.
For example, the following code segment shows how to create a new control to specify the
initial x-velocity of a body called Circle (assume Circle has been declared and defined as a
valid WMBody object):
Dim Slider as WMInput
Set Slider = WM.ActiveDocument.NewInput()
Circle.VX.Formula = "input["+str$(Slider.ID)+"]"
The third line above warrants an explanation. Typically, you would specify an expression
such as "input[5]", but the ID number of the Input just created may not be necessarily 5.
The ID property of the WMInput object retains the number, and the number is converted to a
string by the str$ function. Finally, the number is concatenated with "input[" followed
by "]" to create a valid Working Model formula expression.
Changing the Input Value
An input control in Working Model is a flexible tool which allows you to change its value
while the simulation is running. In interactive operation, the user moves the slider bar to
change the input values. In scripting operation, you can simply modify the Value property of
the WMInput object to change the value. The Value property holds values of type Double.
For example, the following line sets the slider value of a WMInput object called Slider to be
5.5.
Slider.Value = 5.5
Putting it All Together: A Simple WM Basic
Program
Now that you know the fundamental elements of Working Model Basic, we will walk you
through a simple WM Basic program.
Spring-Mass Simulation
The following code performs the following tasks:
1. Creates a new Working Model document.
2. Creates a disk.
3. Attaches a spring to the disk.
4. Creates an input slider to specify the downward initial velocity of the
disk.
4. Creates a meter to measure the y position and velocity of the disk.
5. Runs the simulation for 50 frames and exports the meter data to a file.
6. Closes and saves the document.
Most of the functions are derived from examples provided in the preceding sections in the
current chapter.
Sub Main()
' Declare objects
Dim Doc as WMDocument
Dim Disk as WMBody
Dim Spring1 as WMConstraint