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• # Chapter 22: Using Formulas in Carrara

Carrara allows you to create mathematical formulas that in turn create custom features. Using formulas, you can define your own objects, deformers, tweeners, shaders, gels, backgrounds, and backdrops. The interface for creating formulas is common for all items. The valid input and output variables differ for each item you create. Formula editing becomes technical quickly. Higher math or programming experience is recommended.

This chapter describes the following:

• How to use a formula item
• The Formula Editor interface
• Supported functions, operators, constants, and parameters
• The valid input and output variable for each formula item.

## Creating Formula Items

The method for creating a formula item depends on the item you want to create. You can create the following items using formulas:

• Primitive objects
• Deformers
• Tweeners
• Gels
• Backgrounds and Backdrops

To create a Formula primitive:

1. Drag the Formula Primitive icon into the scene, or choose Insert menu > Formula.
2. Double-click the object to display the formula controls, or click the Model room button.

To create a Formula deformer:

1. Click the Properties tray: Modifiers tab.
2. Choose Formula from the pop-up. The formula controls appear in the Modifiers section.

To create Formula tweeners:

1. Double-click the gap between key events on the time track. Carrara opens the Transition Options dialog.
2. Choose Formula from the pop-up. The formula controls appear in the Transition Options dialog.

1. Display the Shader Tree Editor by double-clicking a shader in the Browser.
2. Select the shader tree component where you want to use a formula.
3. Select Pattern Functions> Formula from the list. The formula controls appear on the selected branch of the shader tree.

To create Formula gels:

1. Select a light other than Distant light.
2. Display the Properties tray: Effects tab: Gel panel.
3. Choose Formula from the list. The formula controls appear in the dialog.

To create Formula backgrounds or backdrops:

1. In the Properties tray, select the scene, then click the Effects tab.
2. Select Background or Backdrop.
3. From the (Background or Backdrop) pop-up, choose Formula. The formula controls appear in the Effects section in the Background or Backdrop controls.

### Formula Controls

The formula controls include a readout of the formula itself, sliders for adjusting parameters, a Parse button, and a More button.

Use the Formula Editor controls to enter formulas and set variables.

For a few items, the controls also include a preview of sorts. (For the tweener formula, the preview is a graph.)

The formula editor for tweeners displays a preview of the formula as a graph.

### Editing Formulas

To create or edit a formula:

1. In the formula controls, click More. Carrara opens the Formula Editor.
• You can type into the window to build your formula. Be careful, the editor is case-sensitive.
• Each statement must end with a semicolon.
1. When you are finished in the Formula Editor, click OK.
2. In the formula controls, click the Parse button. Parsing compiles the formula to run.
3. If appropriate to this formula, you can adjust the parameter sliders.

### Formula Operators

 sin(x) sine of x cos(x) cosine of x tan(x) tangent of x asin(x) arcsine of x acos(x) arccosine of x atan(x) arctangent of x atan2(y,x) arctangent of y/x sinh(x) hyperbolic sine of x cosh(x) hyperbolic cosine of x tanh(x) hyperbolic tangent of x sqrt(x) square root of x pow(x,y) x raised to the power of y exp(x) exponential log(x) logarithm log10(x) base-10 logarithm floor(x) floor of x (The largest integer that is less than or equal to x) ceil(x) ceiling of x (The smallest integer that is greater than or equal to x) abs(x) absolute value of x mod(x,y) x modulus y

### Comparison Operators:

 < less than ⇐ less than or equal to == equal to != not equal to > greater than >= greater than or equal to && logical “and” || logical “or”

### Conditional:

variable=1)

For example:

a=((b>1)?1:b);

The expression (b>1) is the comparison. If it's true, the formula returns a=1. If it's false, the formula returns a=b.

PI

E

### Animatable Input Parameters

p1, p2, p3, p4

These parameters can be set between -1 and +1.

### Variables

The variables valid for a particular item depend on its type. Refer to the section below that describes the variables for the formula item you are creating. To define a variable, just use it. Its initial value will be 0.

#### Output Variables

value (output is a grey level) or red, green, blue (output is a color)

The expected output is between 0 (black) and 1 (white or color maximum intensity).

You can use any of these output variables, however, the program can't use `value' and any of `red', `green', and `blue' simultaneously. If the shader is used in a color based channel, then color output variables will have priority (meaning if `value' and `red' are defined, then only `red' will be used). The opposite applies when using the shader in a value based channel, like Shininess. (If `value' is defined, `value' will be used).

#### Input Variables

 u and v These are parametric mapping coordinates. x, y and z These are the local space coordinates of the point being shaded. nx, ny and nz These are the normal local coordinates (normalized vector). X, Y and Z These are the global space coordinates of the point being shaded. NX, NY and NZ These are the normal global coordinates (normalized vector).

### Formula Deformer

The Formula Deformer iterates on all the points of an object, deforming them one by one.

#### Output Variables:

dx, dy and dz The local coordinates of the deformed point. The range is -1 to +1 (0 is the center.)

#### Input Variables:

x, y, z The local coordinates of the point to be deformed.

### Formula Tweener

value

#### Input Variables

t, tmin, tmax t is time. One t unit is 1/1800th of a second. t is between tmin and tmax.

### Formula Backdrop

#### Output Variables

value or red, green, blue

#### Input Variables

u,v (u,v) defines a point on the backdrop. The range is between 0 and 1. (0,0) is the lower left corner, (1,1) the upper right.

### Formula Background

#### Output Variables

value or red, green, blue

#### Input Variables

x,y,z (x,y,z) is the global coordinates of the direction vector, from the camera eye to the background. The vector (x,y,z) is normalized and each coordinate ranges between -1 and +1.

### Formula Gel

#### Output Variables

value or red, green, blue

#### Input Variables

u,v (u,v) defines a point on the backdrop. The range is between 0 and 1. (0,0) is the lower left corner, (1,1) the upper right.

### Formula Primitive (Object)

#### Output Variables

x,y,z local coordinates of the point defined by (u,v).

#### Input Variables

u,v The parametric space coordinates. The range is between 0 and 1.

1)
comparison)?(value if TRUE):(value if FALSE

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