Using KActors

Overview

Dynamic elements can bring life to game environments and provide an added aspect of realism for the player. Objects driven by real-time rigid body physics simulations can be added using the KActor. This actor uses a single StaticMesh asset and can be pushed or moved around using forces from weapon fire, special force actors, and even by the player. These are great for adding items such as crates or barrels placed around the map but can also be used for more complex effects like doors that can be pushed open, swinging lights; practically any physics-driven effect.

Placement

KActors are placed in maps using the right-click context menu of the viewports.

Note: A StaticMesh asset must have simplified collision geometry in order to be used with a KActor.

Context Menu

1. In the Content Browser, select the StaticMesh you want to add to the map as a KActor.
   
2. Right-click in the viewport where you want to add the mesh and choose Add RigidBody: [MeshAssetPath] from the context menu. The location does not need to be exact. You can always reposition, rotate, scale the mesh afterwards.
   
3. The StaticMesh has been placed in the map as a KActor, as seen in the Property Window.
   

KActor Setup

After placing a KActor in the level, there are properties that may need to be adjusted to get the object to behave properly.

Conversion to/from Other Actors

KActors can be converted to and from certain other types of actors which display a StaticMesh through the right-click context menu of the viewports. This can be handy should you decide that you want a mesh previously placed in the map as a StaticMeshActor or InterpActor to be a KActors, or vice-versa.

Converting to a KActors

1. In the viewport, select the actor you want to convert to a KActors.
   
2. Right-Click on the actor and choose *Convert > Convert [CurrentActorType] to KActors.
   
3. The actor has been converted to a KActor, as seen in the Property Window.
   

Converting from a KActor

The process of converting from a KActor to another type is the same as the process for converting to a KActor shown above. The types of actors that a KActor can be converted to are listed below:

• StaticMeshActor
• Mover (InterpActor)

Material Override

The Material(s) applied to a StaticMesh can be overridden on a per-actor basis. This allows a single StaticMesh asset to be used multiple times in a single map or throughout your game while giving each a unique appearance. The Materials property located in the Rendering category of the StaticMeshComponent of the KActor is an array of Materials that directly maps to those applied to the StaticMesh asset through the Static Mesh Editor. Materials can be assigned to the array manually or they can be applied directly to the mesh in the viewport by dragging and dropping from the Content Browser.

Manual Assignment

1. In the viewport, select the KActor you want to assign a new Material to and press F4 to open its properties in the Property Window.
   
2. In the Rendering category of the StaticMeshComponent under DynamicSMActor, add a new item to the Materials array by clicking the button. If the StaticMesh has more than one material slot, you may need to add more than one item as the items in the array match the material slots of the StaticMesh.
3. In the Content Browser, select the Material you want to apply to KActor in the map.
   
4. Press the button for the corresponding item in the Materials array to assign the material. The mesh is now displayed with the Material applied.
   

Drag and Drop

1. In the Content Browser, locate the Material you want to apply to KActor in the map.
   
2. Left-Click on the Material in the Content Browser and drag the mouse (while holding the left mouse button down) from the Content Browser to the section of the KActor in the viewport you want to apply the Material to.
   
3. Release the left mouse button to apply the Material. The mesh is now displayed with the Material applied and the Materials array in the Property Window has been updated.
   

Physical Material

The physical properties that control how the KActor interacts dynamically with the world come from the PhysicalMaterial applied to the StaticMesh asset. Aspects of the physical simulation such as density, friction, damping, etc. are all configurable through PhysicalMaterials. In addition, PhysicalMaterials provide the ability to specify sounds and particle effects to be played on various collision events, such as impacts and sliding along surfaces.

Overriding Physical Materials

This PhysicalMaterial can be overridden on a per-actor basis by assigning a new PhysicalMaterial to the StaticMeshComponent of the KActor.

1. In the viewport, select the KActor you want to assign a new PhysicalMaterial to and press F4 to open its properties in the Property Window.
   
2. In the Content Browser, select the Material you want to apply to KActor in the map.
   
3. In the Physics category of the StaticMeshComponent under DynamicSMActor, press the button for the PhysMaterialOverride property to assign the PhysicalMaterial.
   

Constraints and KActors

KActors can be bound to each other or to the world in order to limit or control how they are able to move through the use of constraints. These actors can limit the movement or rotation of KActors along specific axes to create things like hinges, ball and socket joints, or pulleys, or even drive the movement or rotation to create springs or motors.

See the Physics Constraint Reference for more information and descriptions for all constraint properties.

Constraining a KActor

1. In the Actor Classes browser, select the type of constraint you wish to use.
   
2. In the viewport, right-click in the location you want to place the constraint and choose Add [ConstraintType] Here. You can always reposition and rotate the constraint after placing it.
   
3. Select the constraint and press F4 to view its properties. Press the Lock Selected Actors button to lock the Property Window.
   
4. Select the KActor and then press the button for the ConstraintActor1 property in the RB Constraint Actor category. A red bounding box is displayed around the KActor to show it has been constrained to the ConstraintActor1 property. A blue box would be displayed for an actor constrained to the ConstraintActor2 property.
   
   The ConstraintActor2 property is left empty. This constrains the KActor to the world at the location of the constraint actor.
5. Set the desired properties on the constraint. This example has limited the rotation solely to 90 degrees around the twist axis.
   
6. Testing the constrained KActor in-game, it now swings when a force is applied.