# `Cauldron3D.Raster`
[🔗](https://github.com/jaman/cauldron/blob/v0.2.2/cauldron_3d/lib/cauldron_3d/raster.ex#L1)

Draws prepared polygons (`Cauldron3D.Setup`) into rows of pixels.

Each row keeps the runs of pixels where one polygon is nearest; a polygon added to the
row takes the pixels where it is nearer than what is there, found from its `:near`
plane, so every pixel is painted once, by the polygon in front, whatever order the
polygons come in. Where two are equally near the one added first keeps the pixel.
See-through, blended and always-on-top setups (`Cauldron3D.Setup.overlay?/1`) are
painted after, over the row: first the unblended, in the order given, each pixel taken
where it is nearer than what is there and its alpha passes, keeping its own nearness;
then the blended, in the order given, mixed over what is there where they are nearer,
leaving the nearness as it was. In a picture in full colour the depth test reads the
nearness of every overlay already drawn; in an indexed picture only that of the runs.

    Cauldron3D.Raster.rows(setups, 0..199, width, paint_context)
    #=> binary of 200 rows

# `run`

```elixir
@type run() :: {non_neg_integer(), non_neg_integer(), Cauldron3D.Setup.t()}
```

# `rows`

```elixir
@spec rows(
  [Cauldron3D.Setup.t()],
  Range.t(),
  pos_integer(),
  Cauldron3D.Paint.context()
) :: binary()
```

The pixels of `rows` (a range of row numbers) in a picture `width` wide, every row in
turn, with `context` handed to `Cauldron3D.Paint.span/6`.

# `runs`

```elixir
@spec runs([Cauldron3D.Setup.t()], integer(), pos_integer()) :: [run()]
```

The visible runs of row `y`, left to right, as `{first, last, setup}`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*