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.
- Update Dependencies
- This will force an update for the Driver Value dependencies.
- Remove Driver
- Removes the driver from the property.
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.
- 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.
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.
- Floating point and decimal integer.
not, conditional operator/ ternary if
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.
Variable are references to properties or delta transformations which are a reference to two properties.
- Add Variable
- Adds a new Driver Variable.
- Uses the copy of the current variable stack so it can be pasted onto another object’s variable stack.
- 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.
- 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 of the object. For example: Cube, Armature, Camera.
- ID of the Armature bone. For example: ”Bone”, ”Bone.002”, ”Arm.r”. This option is for armatures.
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.
- World Space, Transform Space, Local Space.
- Rotational Difference
- Use the rotational difference between two objects or bones.
- Use the distance between two objects or bones.
- Shows the value of the variable.