BVH frustum culling, sidecar cache, per-model buffers, progressive upload

Phase 2 performance: BVH acceleration with median-split build, per-model trees, and EBO re-sorting for GPU cache coherence. Raw binary .ifcview sidecar stores full geometry + BVH for instant subsequent loads (skip tessellation entirely). Per-model GPU buffers (VAO/VBO/EBO per model) eliminate cross-model buffer copies on growth. Sidecar reads happen on a background thread. Bulk GPU uploads are progressive (48 MB/frame chunks) so the viewport stays interactive while multi-GB models stream in. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-09-20 15:08:51 +00:00 · 2026-04-12 09:09:32 +10:00
parent 5b4c1089cf
commit 1dace18d26
9 changed files with 1541 additions and 327 deletions
@@ -0,0 +1,75 @@
+/********************************************************************************
+ *                                                                              *
+ * This file is part of IfcOpenShell.                                           *
+ *                                                                              *
+ * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ * it under the terms of the Lesser GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3.0 of the License, or          *
+ * (at your option) any later version.                                          *
+ *                                                                              *
+ * IfcOpenShell is distributed in the hope that it will be useful,              *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of               *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 *
+ * Lesser GNU General Public License for more details.                          *
+ *                                                                              *
+ * You should have received a copy of the Lesser GNU General Public License     *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
+ *                                                                              *
+ ********************************************************************************/
+
+#ifndef BVHACCEL_H
+#define BVHACCEL_H
+
+#include <cstdint>
+#include <vector>
+#include <unordered_map>
+#include <unordered_set>
+#include <memory>
+
+struct ObjectDrawInfo {
+    uint32_t index_offset;  // byte offset into EBO
+    uint32_t index_count;   // number of indices
+    uint32_t model_id;      // which model this object belongs to
+    float aabb_min[3];      // world-space AABB
+    float aabb_max[3];
+};
+
+static constexpr uint32_t BVH_MAX_LEAF_SIZE = 8;
+static constexpr uint32_t BVH_MIN_OBJECTS = 32;
+
+struct BvhNode {
+    float aabb_min[3];
+    float aabb_max[3];
+    uint32_t right_or_first; // interior: right child index (left is always this_index+1); leaf: first object index
+    uint16_t count;           // 0 = interior; >0 = leaf with this many objects
+    uint16_t axis;            // split axis (0/1/2) for interior; unused for leaf
+};
+static_assert(sizeof(BvhNode) == 32, "BvhNode must be 32 bytes for cache alignment and sidecar format");
+
+struct ModelBvh {
+    uint32_t model_id = 0;
+    std::vector<BvhNode> nodes;
+    std::vector<uint32_t> object_indices;  // indices into object_draw_info_
+};
+
+struct BvhSet {
+    std::unordered_map<uint32_t, ModelBvh> models;
+    std::unordered_set<uint32_t> bvh_model_ids;
+};
+
+struct EboReorderResult {
+    std::vector<uint32_t> reordered_ebo;
+    std::vector<ObjectDrawInfo> reordered_draw_info;
+};
+
+// Build BVH trees for all models in the given draw info snapshot.
+// Only builds the tree structure; does not touch EBO data.
+std::shared_ptr<BvhSet> buildBvhSet(const std::vector<ObjectDrawInfo>& draw_info);
+
+// Reorder the EBO so objects within each BVH leaf are contiguous.
+// Must be called with the CURRENT run's EBO and draw_info (not cached).
+EboReorderResult reorderEbo(const BvhSet& bvh_set,
+                            const std::vector<ObjectDrawInfo>& draw_info,
+                            const std::vector<uint32_t>& original_ebo);
+
+#endif // BVHACCEL_H