game/src/Game/GameSession/ProvinceIndexSampler.gdshaderinc


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// Province shape texture
uniform sampler2DArray province_shape_tex : repeat_enable, filter_nearest;
// Province shape subdivisions
uniform vec2 province_shape_subdivisions;

// Convert a vector of 3 normalised floats to a vector of 3 unsigned bytes
uvec3 vec3_to_uvec3(vec3 v) {
   return uvec3(v * 255.0);
}

// Create a uint triplet describing the province and terrain data at a map-space UV coordinate:
// (u, v) -> (province index bottom byte, province index top byte, terrain index byte)
uvec3 read_uvec3(vec2 uv) {
   uv *= province_shape_subdivisions;
   vec2 subdivision_coords = mod(floor(uv), province_shape_subdivisions);
   float idx = subdivision_coords.x + subdivision_coords.y * province_shape_subdivisions.x;
   return vec3_to_uvec3(texture(province_shape_tex, vec3(uv, idx)).rgb);
}

// Combine a (lower byte, upper byte) uint pair into a single 2-byte uint
uint uvec2_to_uint(uvec2 v) {
   return (v.y << 8u) | v.x;
}