Cairn

    Scenes and entities

    Entities

    An entity is one thing in a scene. Every entity has:

    • a name, shown in the hierarchy
    • a tag, for finding groups of entities from scripts
    • a layer from 0 to 31, which decides what it collides with
    • a transform: position, rotation (Euler angles in degrees) and scale, all relative to its parent
    • a parent, or none for an entity at the top level

    An entity moves with its parent. Make a table the parent of its legs and moving the table moves all of it.

    Untick Active to switch an entity off. It and everything under it is then as good as not there: not drawn, no physics body, no sound, and its scripts stop updating. It keeps its place and its values, and comes back as it was. In the hierarchy it is shown faded. Use it for a door that is not there yet, a menu that is closed, or to try a level without something.

    An entity that is switched off: faded in the hierarchy, with the box by its name unticked

    Tick Persistent on a top-level entity to keep it, with its children and running scripts, when a script switches to another scene.

    Components

    Components give an entity its behaviour. Add them from Add component in the inspector.

    ComponentWhat it does
    CameraThe view the scene is drawn from. The first one marked Primary is used
    Mesh RendererDraws a mesh, with one material per part
    Skinned Mesh RendererDraws a mesh that a skeleton bends
    Directional, Point and Spot LightLight the scene
    SkyAn HDR image as the background and as light
    RigidbodyMakes the entity a physics body
    Box, Sphere, Capsule and Mesh ColliderGive a body its shape
    Character ControllerMoves the entity as a game character does
    JointTies two bodies together
    ScriptsLua or TypeScript scripts, with their fields
    AnimatorPlays animations on a skinned mesh
    Particle SystemSmoke, sparks, dust
    Audio Source and Audio ListenerPlay sounds, and hear them
    UI Canvas and UI ElementScreen UI: text, buttons, sliders
    TextWords in the world

    Components shows each one in the editor and says what every field does. The scripting API reference lists what scripts can read and set.

    Conventions

    • Right-handed, with +Y up.
    • An entity faces down its own -Z axis. So do cameras and lights.
    • Colours in components are linear RGB.
    • Light intensity is not in physical units. A directional light at 3 is a bright day.

    Scenes

    A scene is a file with the .cairnscene extension. Ctrl+S saves the open one.

    To make a scene, use New > Scene in the Assets panel. To open one, double-click it there.

    The scene a game starts with is set in Project settings.

    Render settings

    Each scene has its own exposure, bloom, anti-aliasing and ambient occlusion settings. Click an empty part of the viewport so that nothing is selected, and the inspector shows them. An agent uses the scene.settings command.

    Limits to know about

    • A scene draws at most 16 lights. Extra ones are skipped with a warning.
    • Only the first directional light with shadows on casts cascaded shadows. Point and spot lights share twelve shadow maps: one per spot light, six per point light.
    • A material with alpha mode Blend is drawn as opaque for now.