Drivers Panel

Reference

Editor

Graph editor

Mode

Drivers

Panel

Properties region ‣ Drivers ‣ Drivers

../../_images/animation_drivers_drivers-panel_panel.png

Drivers panel.

This panel is located in the Graph Editor with the mode set to Drivers.

The Drivers panel is for setting up Driver Variables or a Scripted Expression which will determine the value of the Driver Value.

Settings

Update Dependencies

This will force an update for the Driver Value dependencies.

Remove Driver

Removes the driver from the property.

Type

There are two categories of scripts: built-in (average, sum, minimum and maximum) and custom scripts (Scripted Expressions).

Average Value

Uses the average value of the referenced Driver Variables.

Sum Values

Uses the sum of the referenced Driver Variables.

Scripted Expression

Uses a Scripted Expression. See Expression. You can write a Python expression which performs your own calculations on the Driver Variables.

Minimum Value

Uses the lowest value from the referenced Driver Variables.

Maximum Value

Uses the highest value from the referenced Driver Variables.

Show Debug Info

Shows the Driver Value.

Driver Value

The output value of the driver script.

Expression

Expression

Here you can add variables, real numbers, math operators, math functions, Python properties, driver functions. See Driver Expression below for some examples. For performance optimization it is best to use the Simple Expressions subset as much as possible.

Use Self

This allows for drivers to references their own data using the variable self. Useful for objects, bones, to avoid having to create a variable pointing to its self.

Simple Expressions

Blender can evaluate a useful subset of Python driver expressions directly, which significantly improves performance, especially on multi-core systems. To take advantage of this, the driver expression must only use the following features:

Variable Names

Use only ASCII characters.

Literals

Floating point and decimal integer.

Globals

frame

Constants

pi, True, False

Operators

+, -, *, /, ==, !=, <, <=, >, >=, and, or, not, conditional operator/ ternary if

Functions

min, max, radians, degrees, abs, fabs, floor, ceil, trunc, int, sin, cos, tan, asin, acos, atan, atan2, exp, log, sqrt, pow, fmod

Simple expressions are evaluated even when Python script execution is disabled.

When an expression outside of this subset is used, Blender displays a ”Slow Python expression” warning.

Driver Variables

../../_images/animation_drivers_drivers-panel_transform-channel2.png

Transform channel setup.

../../_images/animation_drivers_drivers-panel_distance.png

Distance setup.

Variable are references to properties or delta transformations which are a reference to two properties.

Add Variable

Adds a new Driver Variable.

Copy/Paste

Uses the copy of the current variable stack so it can be pasted onto another object’s variable stack.

Name

Name to use for scripted expressions/functions. No spaces or dots are allowed and must start with a letter.

Variable Type

The type of variable to use.

Single Property

Use the value from some RNA property. For example, the Ambient shading color from a material. (see Fig. Setup of a single property.) First select the type of ID-block, then the ID of the ID-block, then copy and paste an RNA property Ctrl-V. See also Custom Properties.

ID Type

The ID-block type. For example: Key, Image, Object, Material.

ID

The ID of the ID-block type. For example: ”Material.001”.

RNA Path

The RNA ID name of the property. For example: ’ambient’ from material shading.

Transform Channel

Use one of the Transform channels from an object or bone.

ID

ID of the object. For example: Cube, Armature, Camera.

Bone

ID of the Armature bone. For example: ”Bone”, ”Bone.002”, ”Arm.r”. This option is for armatures.

Type

For example, X Location, X Rotation, X Scale.

The Average Scale option retrieves the combined scale value, computed as the cubic root of the total change in volume. Unlike X/Y/Z Scale, this value can be negative if the object is flipped by negative scaling.

Space

World Space, Transform Space, Local Space.

Rotational Difference

Use the rotational difference between two objects or bones.

Distance

Use the distance between two objects or bones.

Value

Shows the value of the variable.

Example

../../_images/animation_drivers_drivers-panel_single-property.png

Setup of a single property.