Using Drivers And Keyframes To Animate Material Properties In Blender

What are Material Drivers?

Material drivers in Blender are a way to control material properties through relationships with other objects. They allow material attributes like color, emission strength, alpha, and more to be animated based on transforms, constraints, and properties of other scene elements. This avoids the need to manually insert keyframes for animation.

Drivers set up relationships where changing one object’s property automatically changes a material property based on a scripted expression. For example, the emission strength of a material could be driven by the Z location of an empty object, increasing as the empty moves higher. This allows complex animated effects without tedious manual animation of every material property.

Using Drivers to Control Material Properties

Setting up a material driver is straightforward through the UI. After adding an appropriate data property to drive, right click on the material property to animate. In the context menu, select “Add Driver” then edit the driven property’s value field. This will allow a Python expression to be entered using variables from scene objects.

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For example, to have a material’s hue driven by an empty’s X rotation:

Add an Empty object to the scene and parent the object with the target material to it (for visibility)
In the Material properties, show Color attributes then enable Hue
Right click on Hue and select Add Driver
In the Hue value field, enter: var * empty.rotation_euler.x

Where “empty” is the name of the empty object and var (by default) is a factor of 1. This will make the hue rotate matching the empty’s X rotation. More complex scripts and relationships are possible for accurate color cycling.

Working with Keyframed Animations

In contrast to drivers, keyframed animation requires manually setting values for material properties at different times. Blender interpolates between the defined keyframes to animate the property. This gives direct control compared to drivers.

For example, to animate emission strength flickering over time:

Add an Emission node the Material nodes
In the Timeline, move to the start frame
Set Emission Strength to 0 and press I while highlighted to set a keyframe
Move to the end frame and set Strength to 5, adding another keyframe

This will animate the strength between 0 and 5 based on the keyframes. More keyframes can be added to fine tune the animation over time.

Combining Drivers and Keyframes

The power of drivers and keyframes comes from combining them. This makes it possible to set base animated properties with keyframes, then modulate those animations further with drivers.

For example, the emission strength can be keyframed to flicker randomly. Then drivers could control overall strength based on proximity to other scene elements. Here is one approach:

Keyframe base flickering emission over time with different strength values
Add driver to modify underlying emission strength based on distance to target empty
Use a script like: var * (1.0 – min(empty.location.x / 10, 1))

This will cause emission to drop off as empty moves further left, up to 10 units away, while still flickering from keyframes. Many creative effects can be achieved by layering drivers over keyframe animations.

Frequently Asked Questions

My driver changes too abruptly, how can I smooth it out?

Try modifying the driver script to increment more gradually using math nodes like Nod or Mix. Keyframing transitions between larger steps can also help blend driver changes.

Is there a way to visualize or debug drivers?

Yes, enabling the graph editor allows the driver curves and relationships to be inspected. Sampled values and edits can be viewed here before rendering.

How can I tell if a material property is being driven vs keyframed?

Right click the property and choose “Copy as new driver” – if this is enabled, it means no driver exists yet. Properties with F-curves in graph/timeline are keyframed.

Additional Resources

For more information on animating with drivers and keyframes in Blender, refer to:

These cover the basics as well as more advanced driver techniques for realistic lip sync, fluids, blend shape mixing, and inter-property relationships.

Example Animations

Here are some example .blend files making use of material drivers and keyframes:

EmissionFlicker.blend: Demonstrates self-contained keyframed emission strength flickering on a cube. Download Blend File

HueRotateCube.blend: Rotates a cube’s emission hue based on Empty transform using drivers. Download Blend File

EmissiveProximityMesh.blend: Uses drivers to dim emission on multiple objects as they move away from an empty. Download Blend File

These examples contain annotated node groups breaking down the exact driver and keyframing setups used in their materials. Readers are encouraged to download them and inspect how they work by opening them in Blender. The techniques can be extracted and expanded upon.