geometry.hpp

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#pragma once
 
#include <fcb/error.hpp>
#include <fcb/span.hpp>
 
#include <cstdint>
#include <string>
#include <vector>
 
#ifdef FCB_WITH_JSON
#    include <nlohmann/json.hpp>
#endif
 
namespace fcb {
 
using UIntView = span<const std::uint32_t>;
 
enum class GeometryKind : std::uint8_t {
    MultiPoint = 0,
    MultiLineString = 1,
    MultiSurface = 2,
    CompositeSurface = 3,
    Solid = 4,
    MultiSolid = 5,
    CompositeSolid = 6,
    GeometryInstance = 7,
};
 
#ifdef FCB_WITH_JSON
 
// ---------------------------------------------------------------------------
// NESTING DEPTH COMES FROM THE GEOMETRY TYPE, NEVER FROM THE ARRAYS.
//
// The format stores a dimensional hierarchy as parallel count arrays:
// `solids[i]` = shells in solid i, `shells[i]` = surfaces in shell i,
// `surfaces[i]` = rings in surface i, `strings[i]` = vertex indices in ring i,
// and `indices` is the flat vertex-index list. Those arrays are AMBIGUOUS: a
// `Solid` with one shell and a `MultiSolid` with one solid flatten to
// byte-identical arrays, so no test over them can tell the two apart. Only
// `Geometry.type()` can, and every decoder below takes it.
//
// The depths, from `geomprimitives.schema.json` and CityJSON 2.0 §6 --
// identical to the table at the top of geom_decoder.rs:
//
//   type                               boundaries  semantics  material  texture
//   MultiPoint                                  1          1  forbidden forbidden
//   MultiLineString                             2          1  forbidden forbidden
//   MultiSurface, CompositeSurface              3          1          1        3
//   Solid                                       4          2          2        4
//   MultiSolid, CompositeSolid                  5          3          3        5
//
// An earlier version of this file dispatched on the outermost populated array
// and collapsed a single-element level into that element. That inference cost
// a nesting level on every one-solid MultiSolid and CompositeSolid, in both
// `material.values` and `texture.values`; see conformance/inputs/
// appearance_depths.city.jsonl, which fails for any reader that infers.
// ---------------------------------------------------------------------------
 
nlohmann::json decode_boundaries(GeometryKind type, UIntView solids, UIntView shells,
                                 UIntView surfaces, UIntView strings, UIntView indices);
 
nlohmann::json decode_semantics_values(GeometryKind type, UIntView solids, UIntView shells,
                                       UIntView values);
 
nlohmann::json decode_material_values(GeometryKind type, UIntView solids, UIntView shells,
                                      UIntView vertices);
 
nlohmann::json decode_texture_values(GeometryKind type, UIntView solids, UIntView shells,
                                     UIntView surfaces, UIntView strings, UIntView vertices);
 
#endif  // FCB_WITH_JSON
 
std::string geometry_type_name(std::uint8_t type);
 
}  // namespace fcb