Metal sampler filtering options

Question

In the example below, does it mean that all filtering options (mag_filter, min_filter, ...) are set to linear? I can't find anything in documentation for just "filter".

constexpr sampler textureSampler (filter::linear, address::clamp_to_edge, coord::pixel);

Answer 1

Almost. It fills min_filter and mag_filter, but not mip_filter. It's very unfortunate that it's not documented. However, you can go into metal_texture header from Xcode, and you will see

constexpr METAL_FUNC _sampler_state _build_sampler_state(_sampler_state s, filter flt)
{
  return
  {
    s.s_address_v, s.t_address_v, s.r_address_v,
        static_cast<uchar>(flt), static_cast<uchar>(flt), s.mip_filter_v,
        s.coord_v, s.compare_func_v,
        s.max_anisotropy_v, s.lod_clamp_min_v, s.lod_clamp_max_v,
        s.border_color_v, s.reduction_v,
  };
}

and if you check out _sampler_state

struct _sampler_state
{
  uchar s_address_v;
  uchar t_address_v;
  uchar r_address_v;
  uchar mag_filter_v;
  uchar min_filter_v;
  uchar mip_filter_v;
  uchar coord_v;
  uchar compare_func_v;
  uchar max_anisotropy_v;
  float lod_clamp_min_v;
  float lod_clamp_max_v;
  uchar border_color_v;
  uchar reduction_v;
};

so you can see that it will set static_cast<uchar>(flt) in the mag_filter_v, and min_filter_v.

I think the mip_filter is conceptually different enough that it can't be set with those.