# `Monty.Frameworks.Models.Salience.Strategies.Vocus2.DepthSalience`
[🔗](https://github.com/d-led/ex.tbp.monty/blob/v0.1.0/packages/ex_tbp_monty_core/lib/monty/frameworks/models/salience/strategies/vocus2/depth_salience.ex#L1)

How much a patch of surface stands out in *depth*.

Mirrors
`tbp/monty/frameworks/models/salience/strategies/vocus2/vocus2.py::DepthSalience`.
VOCUS2 is a colour attention model; this is the extension that makes it work
on depth, and it is why a salience config can care about a shape rather than a
colour.

Two details carry the meaning:

  * the depth is first replaced by its **negative logarithm**, so a depth
    difference is read as a *ratio*. On a log scale a step from 10 cm to 11 cm
    is as interesting as one from 1 m to 1.1 m, which is not true of raw
    depth and is what makes a distant object as findable as a near one;
  * a depth of zero means "nothing there", and its negative logarithm is
    minus infinity — Monty maps the infinities to zero. On a log-depth scale
    zero is *above* every real depth, so an empty pixel reads as the nearest
    patch in the view rather than as an absence. That is what the code does,
    it is reproduced here on purpose, and `docs/monty-differences.md` §1.14 records
    why it is probably not what was meant.

Only the brighter side of the difference is kept, because depth has no "dark
side": a log-depth above its surround is a nearer patch, which is salient; a
log-depth below is merely further away.

# `t`

```elixir
@type t() :: %Monty.Frameworks.Models.Salience.Strategies.Vocus2.DepthSalience{
  center_sigma: float(),
  collapse:
    (Monty.Frameworks.Models.Salience.Strategies.Vocus2.Pyramids.Pyramid.t() ->
       [[float()]]),
  max_octaves: pos_integer() | nil,
  n_scales: pos_integer(),
  operating_limits:
    Monty.Frameworks.Models.Salience.Strategies.Vocus2.OperatingLimits.t(),
  surround_sigma: float()
}
```

# `new`

```elixir
@spec new(keyword()) :: t()
```

# `process`

```elixir
@spec process(t(), Monty.Context.t(), [[float()]]) :: [[float()]]
```

The depth salience map: where the surface is nearer than its surroundings.

---

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