茂之钳
80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
#pragma once
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#include "vde/mesh/halfedge_mesh.h"
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#include <vector>
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#include <string>
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namespace vde::brep { class BrepModel; }
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namespace vde::mesh {
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/**
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* @brief Level-of-detail mesh with multiple detail levels
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*
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* Stores a sequence of simplified meshes from highest detail (index 0)
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* to lowest. Screen-space error thresholds determine which level to
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* use for rendering.
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*
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* @ingroup mesh
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*/
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struct LODMesh {
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std::string name;
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/// Meshes from highest detail (index 0) to lowest
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std::vector<HalfedgeMesh> levels;
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/// Screen-space error thresholds for each level (in pixels)
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std::vector<double> thresholds;
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/**
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* @brief Get the appropriate LOD level for a given screen-space error
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*
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* Selects the lowest-detail level whose threshold is ≤ error.
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* Walks thresholds from coarsest to finest.
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*
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* @param error Screen-space error in pixels
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* @return LOD level index (0 = highest detail)
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*/
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[[nodiscard]] int level_for_error(double error) const;
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/**
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* @brief Get the mesh at a specific LOD level (clamped)
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*
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* @param level Desired LOD level
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* @return Reference to the mesh at that level
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*/
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[[nodiscard]] const HalfedgeMesh& mesh_at(int level) const;
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};
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/**
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* @brief Generate LOD meshes from a high-detail mesh
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*
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* Iteratively applies QEM simplification, reducing face count
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* by `reduction_ratio` at each level.
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*
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* @param mesh High-detail input mesh
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* @param num_levels Number of LOD levels (including base)
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* @param reduction_ratio Ratio of faces to keep at each level (0.5 = half)
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* @return LOD meshes with thresholds proportional to level index
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*
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* @code{.cpp}
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* auto lod = generate_lod(high_res, 4, 0.5);
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* int level = lod.level_for_error(screen_error);
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* render(lod.mesh_at(level));
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* @endcode
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*/
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[[nodiscard]] LODMesh generate_lod(const HalfedgeMesh& mesh,
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int num_levels = 3, double reduction_ratio = 0.5);
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/**
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* @brief Generate LOD from B-Rep body (tessellate + simplify)
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*
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* Tessellates the B-Rep body with default deflection, then
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* generates LOD levels via QEM simplification.
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*
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* @param body B-Rep model
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* @param num_levels Number of LOD levels
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* @return LOD meshes
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*/
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[[nodiscard]] LODMesh generate_brep_lod(const brep::BrepModel& body,
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int num_levels = 3);
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} // namespace vde::mesh
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