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Dion Moult
5161b0a3f8
Edge-collapse decimation (meshopt_simplify) returns BIM meshes unchanged due to per-triangle vertex duplication and non-manifold topology. The sloppy voxel-clustering decimator is faster, needs no shadow index welding, and produces good results at the sub-30px LOD1 threshold. Remove the non-sloppy branch, shadow buffer, IFC_LOD_SLOPPY and IFC_LOD_LOCK_BORDER env vars. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
58 lines
3.1 KiB
C
58 lines
3.1 KiB
C
/********************************************************************************
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* *
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* This file is part of IfcOpenShell. *
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* *
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* IfcOpenShell is free software: you can redistribute it and/or modify *
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* it under the terms of the Lesser GNU General Public License as published by *
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* the Free Software Foundation, either version 3.0 of the License, or *
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* (at your option) any later version. *
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* *
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* IfcOpenShell is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* Lesser GNU General Public License for more details. *
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* *
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* You should have received a copy of the Lesser GNU General Public License *
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* along with this program. If not, see <http://www.gnu.org/licenses/>. *
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* *
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********************************************************************************/
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#ifndef LODBUILDER_H
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#define LODBUILDER_H
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#include "SidecarCache.h"
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// Build a LOD1 index slice for every mesh in `sd` whose triangle count is
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// above `min_triangles`, using meshoptimizer's sloppy (voxel-clustering)
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// decimator. The LOD1 indices are appended to `sd.indices`; each MeshInfo's
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// lod1_ebo_byte_offset + lod1_index_count are populated to point at the
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// appended range. Meshes that don't qualify (too small) or where the
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// decimator couldn't meet the target within the error budget have
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// lod1_index_count left at 0 (renderer falls back to LOD0).
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//
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// Defaults match the Phase 3B first-iteration design:
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// min_triangles = 500 — below this the overhead dominates
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// target_ratio = 0.25 — aim for 25% of original tris
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// target_error = 0.05 — stop if relative error exceeds 5%
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//
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// `sd.vertices` is raw bytes at the quantized layout; positions are
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// dequantized per-mesh (using MeshInfo.local_aabb_min/max) into a temp
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// float array before feeding meshoptimizer. Vertices are not modified —
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// LOD1 reuses the same VBO, just with a different index list.
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void buildLods(SidecarData& sd,
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int min_triangles = 500,
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float target_ratio = 0.25f,
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float target_error = 0.05f);
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// Cheap summary for logging. Safe to call before or after buildLods.
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struct LodStats {
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uint32_t meshes_total = 0;
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uint32_t meshes_with_lod1 = 0;
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uint32_t tris_lod0 = 0; // sum across all meshes
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uint32_t tris_lod1 = 0; // only for meshes that got LOD1
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uint32_t tris_lod0_for_lod1 = 0; // LOD0 tris of the meshes that got LOD1
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};
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LodStats summariseLods(const SidecarData& sd);
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#endif // LODBUILDER_H
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