Billboarding

Billboarding is a technique in three-dimensional computer graphics in which flat, two-dimensional elements—typically textured quads or sprites—are oriented to face the viewer. The approach allows simple geometry to convey the appearance of more complex objects, enabling efficient rendering of scenes with many elements such as particles, vegetation, and signage.

Two common forms are spherical billboarding and cylindrical billboarding. Spherical billboarding rotates the billboard freely to face the camera in all directions, ensuring it always looks at the viewer. Cylindrical billboarding rotates around a single axis (usually the vertical axis) so the object remains upright while still facing the camera. A screen-aligned or view-space variant computes orientation in such a way that the billboard directly faces the camera in screen space, preserving consistent legibility.

Implementation typically updates the billboard’s orientation each frame. In world-space billboarding, the model matrix is adjusted so the quad’s forward direction points toward the camera. In spherical billboarding, the rotation is derived to align with the camera’s view vector; in cylindrical billboarding, rotation around the up axis aligns the quad with the view while preserving its vertical orientation. An efficient approach uses the inverse of the camera’s rotation to create a rotation matrix that is then applied to the billboard.

Common applications include particle systems (smoke, fire, rain), distant terrain features, and vegetation such as trees rendered as billboards to reduce polygon counts. Billboards are also used for in-scene text and UI labels. Limitations include simplified lighting and shading, reliance on transparency, and eye-pleasing artifacts if many billboards overlap or if depth sorting is not properly handled.