Camera and Coordinate Systems

Axolotl2D exposes world, screen, and normalized-device coordinates explicitly. Camera2D converts between the game world and the top-left screen coordinate system used by input and UI.

Coordinate conventions

Space	Origin and range	Typical use
World	Defined by your scene	Gameplay objects and maps
Screen	`(0, 0)` at top-left, pixels increase right and down	Mouse input and UI
Normalized device	`(-1, 1)` at top-left, `(1, -1)` at bottom-right	Low-level rendering

CoordinateSpace.World tells SpriteBatch to apply the active camera. CoordinateSpace.Screen submits pixel coordinates without the camera.

Camera position, pan, and zoom

Camera2D.Position is the world point shown at the viewport center. The camera follows game-window resize events and keeps ViewportSize current.

public sealed class CameraController(
    GameObject gameObject,
    Camera2D camera,
    Game game) : Component(gameObject)
{
    public override void Update(double deltaTime)
    {
        var keyboard = game.GetKeyboard();
        if (keyboard is null)
        {
            return;
        }

        var distance = 300f * (float)deltaTime / camera.Zoom;
        if (keyboard.IsKeyPressed(Key.A)) camera.Pan(new Vector2(-distance, 0));
        if (keyboard.IsKeyPressed(Key.D)) camera.Pan(new Vector2(distance, 0));
        if (keyboard.IsKeyPressed(Key.W)) camera.Pan(new Vector2(0, -distance));
        if (keyboard.IsKeyPressed(Key.S)) camera.Pan(new Vector2(0, distance));
    }
}

Assign Zoom directly or zoom around a screen position:

camera.Zoom = 2f;
camera.ZoomAt(1.1f, mouse.Position);
camera.ZoomAt(1f / 1.1f, mouse.Position);

ZoomAt keeps the world point under the supplied screen position fixed. Its factor must be positive. Direct Zoom assignments are clamped to a minimum of 0.01.

Camera2D.Rotation uses radians. Positive values rotate the camera view consistently with the framework's screen coordinate convention.

Convert input to world coordinates

Mouse positions arrive in screen pixels. Convert them before world hit testing or placement:

Vector2 screenMouse = mouse.Position;
Vector2 worldMouse = Coordinates.ScreenToWorld(screenMouse, camera);

projectile.Transform.LocalPosition = worldMouse;

Convert a world position to screen space when placing a UI marker over an object:

Vector2 markerPosition = Coordinates.WorldToScreen(
    target.Transform.Position,
    camera);

Normalized device conversions

Low-level rendering code can use:

Vector2 ndc = Coordinates.ScreenToNormalizedDevice(screenPoint, game.Viewport);
Vector2 screen = Coordinates.NormalizedDeviceToScreen(ndc, game.Viewport);

Most game code should remain in world or screen coordinates. Keep conversions at system boundaries, such as input, UI projection, and custom rendering.

Use a different camera for a batch