Billboards

A billboard or impostor is a flat 2D object (usually a textured quad) that always faces the camera, no matter where the camera moves. It's a common trick used to represent complex visuals with simple geometry.

To render a billboard, add the Billboard function to your Frame context with a billboard material:

Billboard(
    material = billboard {
        colorTexture = texture("textures/sprite.png")
        position = Vec3(3f, 5f, 7f)
        scale = Vec2(2f, 2f)
        rotation = 0.3f
    },
    transparent = true
)

The billboard { ... } block configures BillboardMaterialScope, which extends BaseMaterialScope with all its properties (color, colorTexture, metallicFactor, roughnessFactor, etc.) plus the following:

Property	Type	Default	Description
position	Vec3	(0, 0, 0)	World position of billboard's center
scale	Vec2	(1, 1)	Billboard's size (horizontal/vertical)
rotation	Float	0.0f	Rotation (in radians)
effect	BillboardEffect?	null	Particle effect (fire, fireball, smoke)

Billboard instancing is also supported for rendering many billboards efficiently:

Billboard(
    material = billboard { colorTexture = texture("textures/particle.png") },
    transparent = true,
    instancing = billboardInstancing("particles", 100, true) {
        repeat(100) { i ->
            Instance(pos = ..., scale = ..., rotation = ..., color = ...)
        }
    }
)