Cauldron2D.Projection.Ground (Cauldron2D v0.2.2)

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Samples a textured ground plane in perspective: for each pixel below the horizon the world point it looks at, the tile there, and that tile's texel, faded towards a void colour with distance.

Cauldron2D.Projection.Ground.rows(%{
  grid: grid,
  size: {320, 200},
  tile: 16,
  camera: camera,
  void: {24, 30, 58},
  levels: 6,
  sky: sky
})

A grid is the world made into data the sampler can read without calling back into Elixir: build_grid/3 turns a fn {x, y} -> cell end and a bounding box into one.

The work is done by a NIF where one built and in Elixir where it did not; available?/0 says which. The two answer the same picture but not always the same bytes: a pixel whose world point falls within a last-bit rounding of a texel boundary may take the neighbouring texel, so a handful of pixels a frame can differ, by one level of one channel. Where a tile's texture is one colour the two are identical.

Summary

Types

camera()
grid()

Functions

available?()

Whether the NIF is loaded and the sampling is done in C.

build_grid(cell, arg, arts)

A grid of tile indices for cell over the box {left, top, right, bottom} in tiles, with the textures the indices point at.

rows(spec)

The picture's rows as a map of row index to that row's pixels, the rows at and above the horizon taken from sky and the rest sampled from the plane.

Types

camera()

@type camera() ::
  {float(), float(), float(), float(), float(), float(), float(), float(),
   float(), float(), float()}

grid()

@type grid() :: %{
  cells: binary(),
  bounds: {pos_integer(), pos_integer(), integer(), integer()},
  textures: binary()
}

Functions

available?()

@spec available?() :: boolean()

Whether the NIF is loaded and the sampling is done in C.

build_grid(cell, arg, arts)

@spec build_grid(
  ({integer(), integer()} -> term()),
  {integer(), integer(), integer(), integer()},
  %{
    optional(term()) => pos_integer()
  }
) :: {binary(), {pos_integer(), pos_integer(), integer(), integer()}}

A grid of tile indices for cell over the box {left, top, right, bottom} in tiles, with the textures the indices point at.

arts maps an art to its one-based index; a tile the map does not answer for, or whose art is not in arts, is 0 and drawn as the void.

rows(spec)

@spec rows(map()) :: %{required(non_neg_integer()) => binary()}

The picture's rows as a map of row index to that row's pixels, the rows at and above the horizon taken from sky and the rest sampled from the plane.

Takes :grid, :size, :tile, :camera, :void, :levels and :sky, where sky is a tuple of one four-byte pixel per row. native: false samples in Elixir even where the NIF loaded, which is how the two are checked against each other.