Transform Constraints

UXTools provides a mechanism to implement and apply transform constraints to actors during manipulation. All you need to do is inherit from UUxtManipulatorComponent, as UUxtGenericManipulatorComponent and UUxtBoundsControlComponent for example.

Usage

In order to use constraints:

  1. Add any desired UxtTransformConstraint-derived components to the actor.
  2. Add any UUxtManipulatorComponent-derived components to the actor, such as UUxtGenericManipulatorComponent and UUxtBoundsControlComponent.

Each UUxtManipulatorComponent will apply all constraint components in the actor if bAutoDetectConstraints is set to true. Otherwise, you can fill the SelectedConstraints array to choose which constraints you'd like that component to apply during its interaction.

Implicit scale

There's an implicit constraint which doesn't inherit from UxtTransformConstraint and is applied by all UUxtManipulatorComponents. The reason for that is preventing their scales from reaching 0 or even negative values. Besides that, UUxtBoundsControlComponent avoids having interaction issues with its handles when the scale is too small.

The MinScale and MaxScale properties give you flexibility to configure this behavior within reasonable values, clamped to prevent the unexpected results previously mentioned.

Use bRelativeToInitialScale to configure whether the limits are relative to the scale at interaction start (true) or absolute (false).

In the following example, MinScale is set to 0.3:

Min/max scale constraint demo

Built-in constraint components

There are a few built-in constraint components, which will hopefully save you from having to write your own.

UxtFaceUserConstraint

Makes the actor face the camera while interacting with it.

Set bFaceAway to true to make the object face away from the camera.

Face user constraint demo

UxtFixedDistanceConstraint

Makes the actor stay at a fixed distance from the camera.

With Without
Fixed distance constraint demo Fixed distance without constraint demo

UxtFixedRotationToUserConstraint

Makes the actor maintain the same rotation (relative to the user) that it had when the interaction started.

Set bExcludeRoll to false to allow rolling of the actor.

Fixed rotation to user constraint demo

UxtFixedRotationToWorldConstraint

Makes the actor maintain the same rotation (relative to the world) that it had when the interaction started.

Fixed rotation to world constraint demo

UxtMaintainApparentSizeConstraint

Makes the actor maintain the apparent size (relative to the user) that it had when the interaction started.

Maintain apparent size constraint demo

UxtMoveAxisConstraint

Limits movement on specific axes. Use the ConstraintOnMovement bit mask of EUxtAxisFlags.

Move axis constraint demo

(Example limiting the movement along the X and Z axes)

UxtRotationAxisConstraint

Limits rotation on specific axes. Use the ConstraintOnRotation bit mask of EUxtAxisFlags.

Rotation axis constraint demo

(Example limiting the rotation around the X and Y axes)

Adding more constraint components

If none of the Built-in constraint components suits your needs, you can add more by simply creating a new UCLASS that inherits from UxtTransformConstraint. Then, provide implementations for GetConstraintType, ApplyConstraint and (optionally) Initialize.

In this case, please feel free to take a look at our contributing docs and make a suggestion!