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 * This file is part of IfcOpenShell.                                           *
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 * IfcOpenShell is free software: you can redistribute it and/or modify         *
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 *
 * Lesser GNU General Public License for more details.                          *
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#ifndef LODBUILDER_H
#define LODBUILDER_H

#include "SidecarCache.h"

// Build a LOD1 index slice for every mesh in `sd` whose triangle count is
// above `min_triangles`, using meshoptimizer's sloppy (voxel-clustering)
// decimator.  The LOD1 indices are appended to `sd.indices`; each MeshInfo's
// lod1_ebo_byte_offset + lod1_index_count are populated to point at the
// appended range.  Meshes that don't qualify (too small) or where the
// decimator couldn't meet the target within the error budget have
// lod1_index_count left at 0 (renderer falls back to LOD0).
//
// Defaults match the Phase 3B first-iteration design:
//   min_triangles = 500     — below this the overhead dominates
//   target_ratio  = 0.25    — aim for 25% of original tris
//   target_error  = 0.05    — stop if relative error exceeds 5%
//
// `sd.vertices` is raw bytes at the quantized layout; positions are
// dequantized per-mesh (using MeshInfo.local_aabb_min/max) into a temp
// float array before feeding meshoptimizer.  Vertices are not modified —
// LOD1 reuses the same VBO, just with a different index list.
void buildLods(SidecarData& sd,
               int min_triangles = 500,
               float target_ratio = 0.25f,
               float target_error = 0.05f);

// Cheap summary for logging.  Safe to call before or after buildLods.
struct LodStats {
    uint32_t meshes_total       = 0;
    uint32_t meshes_with_lod1   = 0;
    uint32_t tris_lod0          = 0;   // sum across all meshes
    uint32_t tris_lod1          = 0;   // only for meshes that got LOD1
    uint32_t tris_lod0_for_lod1 = 0;   // LOD0 tris of the meshes that got LOD1
};
LodStats summariseLods(const SidecarData& sd);

#endif // LODBUILDER_H