Transition Rules

Creating Transition Rules

Transition Rules are methods of controlling flow inside a State Machine, and are automatically created along the wires that connect States and Conduits. These Transition Rules can perform any number of checks and tests against variable values, all with the purpose of outputting a true or false value, which then determines whether the animation can move through the transition.

Connecting States or Conduits together can be performed by left-clicking and dragging from one State (or Conduit) to another:

After a connection is made, a Transition Rule appears as a small circular directional icon inside the wired connection:

When you mouse over the icon, a visual indication of what the rule is will be displayed:

In this example, for JumpLoop to transition to JumpEnd, the variable IsInAir? must be NOT true.

Rules can also be set to determine flow for a transition in both directions:

This means that a rule can be set to exit one state then to move to another, and a rule can be applied to transition back to that state.

Editing Transition Rules

Double-clicking a Transition Rule will open a window where you can define the variables that must be met for the transition to occur.

Similar to Blueprints, you can specify variables in the My Blueprint window and drag them into the graph. By connecting the variables to various conditions which are then connected to the Result node, you can define what must be true (or false) for the transition to occur.

For information on getting started with Blueprint, refer to the Introduction to Blueprints documentation.

Transition Rule Details

When you click a Transition Rule, the Details panel will update, and additional options will become available.

Inertialization

Inertial blending is a type of blend; however, the Inertialization system itself does not sample from a source animation. Instead, the velocity and acceleration that are inherent in the motion at the time we begin the switch to the new animation are used to carry forward the motion.

Please see Inertialization for more information on Inertialization usage.

You can enable Inertialization by setting the Blend Logic property in the Details panel to Inertialization.

You can also set the Transition Type to Inertialization on certain Blend Nodes.

You will need to use the Inertialization node to specify where in your AnimGraph the inertial blend is to occur.

The video below illustrates a Standard Blend as well as an Inertial Blend (the playback speed has been altered to illustrate the transition).

In the video above, we use a Standard Blend to blend between animations. Both animations are sampled at the same time and crossfade during the transition.

When we apply Inertialization as the Blend Logic, we add the Inertialization node between the Locomotion and the final output pose. When doing so, the transitions between states are instantaneous, and the motion carries over to the next pose.

Custom Blends

In addition to the nodes cited above, there is also information exposed inside Custom Blend Graphs to allow them to be used for more than just a one-shot, custom-transition animation.

You can also use get nodes that reference the asset players just like a Transition Rule.

If you have an understanding of Animation Programming in Unreal, Native Getters can also be used to improve performance.

Additional Considerations

When working with child Animation Blueprints and overriding animations in a State Machine, animations referenced by transition rules do not have to be the same length in every child Animation Blueprint. When using nodes like the Time Remaining node (which can be used to determine how much time is remaining in an animation and can be used as part of a Transition Rule), these types of nodes correctly respond to changes in animation length when animations are overridden in child Animation Blueprints.

Also, rather than targeting a specific animation as part of your Transition Rule that might change or may be overridden, you can use several class-based get nodes that always pick the highest weighted animation from the source state (pictured below).