screenaligned

Screenaligned is a term used in computer graphics and game development to describe an object or element whose orientation or placement is aligned with the screen’s coordinate system rather than the world’s. In practice, screen-aligned objects maintain a fixed relationship to the viewer’s screen, often appearing to face the camera or to stay upright relative to the screen axes. This concept is closely related to billboarding, where sprites or particles always face the camera, and to user interface overlays that remain readable regardless of camera tilt.

In implementation, screen alignment can be achieved by orienting an object so its local axes coincide with screen axes or by updating its rotation each frame to preserve a screen-based orientation. Techniques include projecting world positions to screen space, computing a rotation to align with the screen plane, or using shaders that render quads in screen space. Common use cases include particles that should remain legible, floating labels or indicators in 3D scenes, and certain HUD elements or overlays that must not rotate with the world.

Considerations and variants:

- Screenaligned objects may still be affected by camera yaw or pitch, depending on the desired effect.

- Alternatives include camera-aligned (facing the camera) and world-aligned (fixed in world space) approaches.

- Performance concerns are generally modest but can influence shader complexity and update frequency.

See also: billboard, screen space, billboarding, UI overlays.