Computing UV map from an atlas texture

atlas-texture-utils.gd

static func compute_uv(atlas_texture):
  var uv_array_region = atlas_texture.get_region()
  var uv_array_size = atlas_texture.get_atlas().get_size()

  # 0.5 is used to get a margin (remove blank pixel due to round)
  var uv_array_00 = (uv_array_region.pos + Vector2(0.5, 0.5)) / uv_array_size
  var uv_array_01 = (uv_array_region.pos + Vector2(0.5, uv_array_region.size.y - 0.5)) / uv_array_size
  var uv_array_11 = (uv_array_region.pos + uv_array_region.size + Vector2(-0.5, -0.5)) / uv_array_size
  var uv_array_10 = (uv_array_region.pos + Vector2(uv_array_region.size.x -0.5, 0.5)) / uv_array_size

  return [uv_array_00, uv_array_10, uv_array_11, uv_array_01]

# Used for shader (when we use atlas texture in shaders)
static func compute_uv_decal(atlas_texture_from, atlas_texture_to):
  var atlas_texture_size = atlas_texture_from.get_atlas().get_size()
  var atlas_texture_from_region = atlas_texture_from.get_region().pos
  var atlas_texture_to_region = atlas_texture_to.get_region().pos

  return (atlas_texture_to_region - atlas_texture_from_region) / atlas_texture_size