WARNING Many plug-ins are available for MAX R3. Some of them are macro-recordable, and others are not, depending on how the developer created the plug-in code. It’s a good idea to ask the developer about recordability and to request MAXScript capabilities in plug-ins.

Working with Variables

Variables are simply containers that hold a value, property, etc. Why do you need variables? To make scripting fluid and customizable. For instance, you can make a script to find out whether the current temperature is hot or cold. This script would compare the current temperature with a certain value. If the current temperature is below, say, 30, it is cold. Doing this as a script, you would have a variable, called temperature, which you would compare to another variable, named cold, and this comparison would tell you if it is cold or not. Using this method, you can easily change the values of either variables and re-run the script over and over.

Variables are also useful because they allow you to know what property you are using, which is convenient when you are working with the name of the property, not the property itself. Suppose you need to access a property in a diffuse map of an object. To do it in MAXScript, you would need to use object.material.diffusemap .property. If you assign a variable = object.material.diffusemap, you will save time using just variable.property in the future.

	NOTE In MAXScript, the equal sign (=) acts as a command; it tells MAX to make the item on the left equal to the item(s) on the right. To find out whether two things are equal, we use a double equal sign (==), which is described in “Comparing Variables” below.

If you compare MAXScript to other programming languages, it is very easy to assign variables in MAXScript. Almost every programming language requires you to declare variables, variable types, even the amount of memory to be used. In MAX-Script, you don’t need to do anything like this.

Assigning Variables

Assigning variables is simply done by entering a value for the variable. And you can use any kind of value—a number, a property, a string of text, etc.

You can use any name for a variable, excluding some names used by MAXScript commands, special characters, and spaces. A variable name can also have numbers, but it must start with a letter. Here are some of the most common types of variables you can assign in MAXScript.

You can assign an integer value to a variable, and later in the script you can assign a different value, which doesn’t need to be an integer. This is different from many programming languages, where you can’t automatically change a variable type once it’s assigned. Very few operations can be done mixing variable types.

Now you will assign some variables so you can see how it’s done in MAXScript:

1.  Open the Listener.

2.  Type x = 1 and press Shift+Enter.

	NOTE Pressing Shift+Enter processes the line and displays the result on the subsequent line in the output/command pane. (Pressing Enter alone moves the cursor to the next line, but only processes the command if the cursor is in the last line.) The number pad Enter key processes the line the same way as Shift+Enter. This process step is called evaluate, and we’ll refer to it this way in the book.

3.  Type y = 2.5 and evaluate.

4.  If you type x and evaluate, MAXScript will display the value of the x variable.

Performing Math Operations

Math operations are performed the same way variables are assigned, simply by typing the math formula, for example, z = x + y.

All math rules are respected in MAXScript, which means that you can use parentheses and the precedence rules. That is, data in parentheses will be evaluated first, then exponential operations, then multiply and divide, and finally, addition and subtraction. Suppose you have the two following examples: 2 * 3 + 4 and 2 * (3 + 4). In the first instance, MAXScript will first calculate 2*3 and then add 4. In the second one, MAXScript will first calculate 3+4 and then multiply the result by 2.

Performing Basic Math Operations

Let’s work with some variables and basic math operations to get a feel for how MAX handles these functions.

© 2000, Frol (selection, edition, publication)