About : This tutorial will explain the reader how to apply basic physics to a piece of geometry.
Target Audience : Unreal Engine 3 users - Beginners
Platform : Unreal Engine 3
Last Update : November 2007
Basics
Creating a physics object is much simpler than one might imagine. Find yourself a nice a and small Staticmesh in a package somewhere, and add it to the world somewhere as a regular Staticmesh (Hold S on keyboard, click a surface). Then, rightclick the Staticmesh you've just added to the world, and go to Convert - to KActor.
Once converted, open up its properties (F4), and in the section KActor, enable bWakeOnLevelStart. You're done! Start up the level, and shoot the object. Provided that the object is small enough, It should move. If it does not, try scaling it down.
To get your KActor to light up, you will need to enable the Dynamic channel on the surrounding lights, as well as bCastCompositeShadow and bCastDynamicShadows. The last two are optionally and may impact performance.
Advanced physics
The default physics applied to a Staticmesh dictates that the smaller the object, the less it weights. If your object does not respond to your attacks, you will either need to scale it down, or apply a Physical Material, which is usually the way to go. Physical Materials allow you to overwrite the default physic settings and manually edit properties like the weight and friction of an object.
A Physical Material is created and stored in the Generic Browser. Go to the Generic Browser, and rightclick an empty space in the right panel. Pick Create New Physical Material. Once created, open up its properties by double clicking it.
The two most important properties given are Density and Friction. Density allows you to control the weight of the material, Friction allows you to simulate as if something is on rubber, or on wheels or ice.
You can apply a Physical Material by entering it in the PhysMaterialOverride property, found in the properties of the KActor in the sections DynamicSMActor - StaticMeshComponent - Physics.
Also, you may want to take a look at the Mass properties found in the properties of the Static Mesh in the Generic Browser. Double click a Static Mesh - Body Setup - MassScale. Tweaking this value gives additional control over the weight of the Static Mesh. PhysMaterial, found in the same area, also allows you to assign a different default Physical Material to the Static Mesh.
Additionally, these same Physical Materials are also used to change the footstep sounds, and other reaction sounds and effects.