CauldronGPU.Billboards (CauldronGPU v0.3.3)

Flat pictures turned to face the camera — sprites, particles, beams seen side on — as one mesh, rebuilt each tick and put under the same mesh id.

{mesh, keys} = CauldronGPU.Billboards.mesh(boards, camera)
materials = Enum.map(keys, &Map.fetch!(materials_by_key, &1))
[{:mesh, handle.id, mesh}, {:instance, 7, %CauldronGPU.Instance{mesh: handle, materials: materials, shadows: false}}]

A board is a map:

:at — {x, y, z} in the renderer's frame (+Y up), the board's anchor point
:size — {width, height} in the same units
:key — what the board is drawn with; boards sharing a key share a mesh part, and mesh/2 answers the keys in part order so the caller can give one material each
:uv — {u0, v0, u1, v1}, the part of the texture shown, u0 on the left and v0 at the top. Default {0.0, 0.0, 1.0, 1.0}; u0 > u1 mirrors the picture
:anchor — :centre (default), the board centred on :at; or :bottom, its bottom edge centred on :at
:upright — true keeps the board's up along +Y, turning it only about the vertical (a standing sprite); false (default) faces the camera fully
:color — {r, g, b, a} bytes the board's material colour is multiplied by (CauldronGPU.Mesh's colors); when no board has one the mesh has no colours
:offset — {right, up}, where the anchor sits on the board from its centre or bottom, in the board's own units. Default {0.0, 0.0}

The mesh is nil when there are no boards.

Summary

Types

board()

Functions

mesh(boards, camera)

The boards as one mesh facing camera, with one part per key, and the keys in part order.

Types

board()

@type board() :: %{
  :at => {number(), number(), number()},
  :size => {number(), number()},
  :key => term(),
  optional(:uv) => {number(), number(), number(), number()},
  optional(:anchor) => :centre | :bottom,
  optional(:upright) => boolean(),
  optional(:offset) => {number(), number()},
  optional(:color) => {byte(), byte(), byte(), byte()}
}

Functions

mesh(boards, camera)

@spec mesh([board()], CauldronGPU.Camera.t()) ::
  {CauldronGPU.Mesh.t() | nil, [term()]}

The boards as one mesh facing camera, with one part per key, and the keys in part order.