mirror of
https://github.com/IfcOpenShell/IfcOpenShell.git
synced 2026-08-17 10:59:17 +00:00
Dion Moult
3015f758ba
Replace i16x2 octahedral normals with i8x2, filling the 2-byte padding after position and saving 4 bytes per vertex. int8 gives ~1.4 deg worst-case angular error — invisible for BIM geometry which is overwhelmingly axis-aligned. 25% VBO reduction; sidecar files shrink ~15% overall (5.4 GB -> 4.6 GB on a 111-model test scene). Bumps sidecar format to v7. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
88 lines
4.0 KiB
C++
88 lines
4.0 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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// NOTE: Sidecar format v3 is being rewritten to v4 (instanced geometry layout).
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// During the instancing rewrite (Commit A) the cache is a no-op: reads always
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// miss and writes always succeed without producing a file. Commit B will
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// re-introduce the on-disk format with MeshInfo + InstanceGpu sections.
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#ifndef SIDECARCACHE_H
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#define SIDECARCACHE_H
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#include "InstancedGeometry.h"
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#include <cstdint>
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#include <optional>
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#include <string>
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#include <vector>
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#include <memory>
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static constexpr uint32_t SIDECAR_MAGIC = 0x49465657; // "IFVW"
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// v5 = MeshInfo extended with lod1_ebo_byte_offset + lod1_index_count (56 B).
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// sd.indices may contain an appended LOD1 index slice for each mesh
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// where meshoptimizer decimation produced useful output.
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// v6 = VBO vertices quantized to 16 B/vertex (pos u16x3 + normal oct i16x2 +
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// color u8x4). Dequant basis is per-mesh MeshInfo.local_aabb_min/max.
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// v7 = VBO vertices shrunk to 12 B/vertex (normal oct i8x2 replaces i16x2,
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// eliminating 2-byte pad + saving 2 bytes on normal).
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static constexpr uint32_t SIDECAR_VERSION = 7;
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static constexpr uint32_t SIDECAR_ENDIAN = 0x01020304;
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// Fixed-size element record. Strings are stored as (offset, length) pairs
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// into a separate string table.
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struct PackedElementInfo {
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uint32_t object_id;
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uint32_t model_id;
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int32_t ifc_id;
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int32_t parent_id;
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uint32_t guid_offset;
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uint32_t guid_length;
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uint32_t name_offset;
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uint32_t name_length;
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uint32_t type_offset;
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uint32_t type_length;
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};
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// Everything needed to display an already-tessellated model without
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// re-running the iterator. v6 schema: instanced + quantized geometry.
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struct SidecarData {
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// Per-model GPU geometry (local coords). Raw VBO bytes at the
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// INSTANCED_VERTEX_STRIDE_BYTES layout (12 B/vertex as of v7).
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std::vector<uint8_t> vertices;
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std::vector<uint32_t> indices;
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// Mesh dictionary and per-instance data.
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std::vector<MeshInfo> meshes; // indexed by local_mesh_id
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std::vector<InstanceCpu> instances; // sorted by mesh_id
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// Element tree metadata.
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std::vector<PackedElementInfo> elements;
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std::string string_table;
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};
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// v4 writer/reader are stubbed for Commit A — no disk I/O happens.
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bool writeSidecar(const std::string& ifc_path,
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const SidecarData& data,
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uint64_t ifc_file_size);
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std::optional<SidecarData> readSidecar(const std::string& ifc_path,
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uint64_t ifc_file_size);
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#endif // SIDECARCACHE_H
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