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Add BVH-based navigation functions to TGeoTessellated #21045

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Add BVH-based navigation functions to TGeoTessellated #21045

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7acc8cf
Add BVH-based navigation functions to TGeoTessellated
sawenzel Jan 21, 2026
dc87a3d
[geom] Fix warnings in bvh/v2 headers.
agheata Feb 3, 2026
98d5515
[geom] Fix warnings in TGeoTessellated
agheata Feb 3, 2026
ebd09b6
[geom] Fix CloseShape handling of the check flag.
agheata Feb 3, 2026
d45f1e4
[geom] Rebuild tessellated BVH after ResizeCenter
agheata Feb 3, 2026
fcf7b4e
[geom] Add BVH blob persistence and use it in TGeoTessellated
agheata Feb 3, 2026
6b18c88
[geom] Support quad facets in TGeoTessellated BVH
agheata Feb 3, 2026
30199d6
Merge branch 'master' into swenzel/tessellated_on_master
agheata Feb 3, 2026
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2 changes: 1 addition & 1 deletion geom/geom/inc/LinkDef1.h
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@
#pragma link C++ class TGeoXtru + ;
#pragma link C++ class ROOT::Geom::Vertex_t + ;
#pragma link C++ class TGeoFacet + ;
#pragma link C++ class TGeoTessellated + ;
#pragma link C++ class TGeoTessellated - ;
#pragma link C++ class TGeoShapeAssembly + ;
#pragma link C++ class TGeoScaledShape + ;
#pragma link C++ class TGeoVolume - ;
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48 changes: 40 additions & 8 deletions geom/geom/inc/TGeoTessellated.h
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Expand Up @@ -60,18 +60,29 @@ class TGeoTessellated : public TGeoBBox {
using Vertex_t = Tessellated::Vertex_t;

private:
int fNfacets = 0; // Number of facets
int fNvert = 0; // Number of vertices
int fNseg = 0; // Number of segments
bool fDefined = false; //! Shape fully defined
bool fClosedBody = false; // The faces are making a closed body
std::vector<Vertex_t> fVertices; // List of vertices
std::vector<TGeoFacet> fFacets; // List of facets
int fNfacets = 0; // Number of facets
int fNvert = 0; // Number of vertices
int fNseg = 0; // Number of segments
bool fDefined = false; //! Shape fully defined
bool fClosedBody = false; // The faces are making a closed body

// for now separate vectors but might be better to group per face
std::vector<Vertex_t> fVertices; // List of vertices
std::vector<TGeoFacet> fFacets; // List of facets
std::vector<Vertex_t> fOutwardNormals; //! Vector of outward-facing normals

std::multimap<long, int> fVerticesMap; //! Temporary map used to deduplicate vertices
bool fIsClosed = false; //! to know if shape still needs closure/initialization
std::vector<unsigned char> fBVHData; // Serialized BVH data for persistence
void *fBVH = nullptr; //! BVH acceleration structure for safety and navigation
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@agheata agheata Feb 2, 2026

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void * is really bad for any future persistence of this structure, and I/O may become very relevant to avoid re-creating it for very large number of triangles. IMO we need to put here the real type, even if it makes the header directly dependent on bvh::v2.

The destructor of the class should delete fBVH

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@silverweed silverweed Feb 4, 2026

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If we put the real type, can we also use a unique_ptr while we're at it?


TGeoTessellated(const TGeoTessellated &) = delete;
TGeoTessellated &operator=(const TGeoTessellated &) = delete;

// bvh helper functions
void BuildBVH();
void CalculateNormals();

public:
// constructors
TGeoTessellated() {}
Expand Down Expand Up @@ -130,7 +141,28 @@ class TGeoTessellated : public TGeoBBox {
/// Reader from .obj format
static TGeoTessellated *ImportFromObjFormat(const char *objfile, bool check = false, bool verbose = false);

ClassDefOverride(TGeoTessellated, 1) // tessellated shape class
// navigation functions used by TGeoNavigator (attention: only the iact == 3 cases implemented for now)
Double_t DistFromOutside(const Double_t *point, const Double_t *dir, Int_t iact = 1,
Double_t step = TGeoShape::Big(), Double_t *safe = nullptr) const override;
Double_t DistFromInside(const Double_t *point, const Double_t *dir, Int_t iact = 1, Double_t step = TGeoShape::Big(),
Double_t *safe = nullptr) const override;
bool Contains(const Double_t *point) const override;
Double_t Safety(const Double_t *point, Bool_t in = kTRUE) const override;
void ComputeNormal(const Double_t *point, const Double_t *dir, Double_t *norm) const override;

// these are trivial implementations, just for debugging
Double_t DistFromInside_Loop(const Double_t *point, const Double_t *dir) const;
Double_t DistFromOutside_Loop(const Double_t *point, const Double_t *dir) const;
bool Contains_Loop(const Double_t *point) const;
Comment on lines +154 to +156
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@agheata agheata Feb 2, 2026

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Since these are for testing purposes only, leaving them in the public interface may not be the best choice. The alternative could be to move these to a test utility, where we can add also some regression tests in future. What about Safety_Loop ?


Double_t Capacity() const override;

private:
// a safety kernel used in multiple implementations
template <bool closest_facet = false>
Double_t SafetyKernel(const Double_t *point, bool in, int *closest_facet_id = nullptr) const;

ClassDefOverride(TGeoTessellated, 2) // tessellated shape class
};

#endif
65 changes: 33 additions & 32 deletions geom/geom/inc/bvh/v2/bbox.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,38 +10,39 @@ namespace bvh::v2 {

template <typename T, size_t N>
struct BBox {
Vec<T, N> min, max;

BBox() = default;
BVH_ALWAYS_INLINE BBox(const Vec<T, N>& min, const Vec<T, N>& max) : min(min), max(max) {}
BVH_ALWAYS_INLINE explicit BBox(const Vec<T, N>& point) : BBox(point, point) {}

BVH_ALWAYS_INLINE BBox& extend(const Vec<T, N>& point) {
return extend(BBox(point));
}

BVH_ALWAYS_INLINE BBox& extend(const BBox& other) {
min = robust_min(min, other.min);
max = robust_max(max, other.max);
return *this;
}

BVH_ALWAYS_INLINE Vec<T, N> get_diagonal() const { return max - min; }
BVH_ALWAYS_INLINE Vec<T, N> get_center() const { return (max + min) * static_cast<T>(0.5); }

BVH_ALWAYS_INLINE T get_half_area() const {
auto d = get_diagonal();
static_assert(N == 2 || N == 3);
if constexpr (N == 3) return (d[0] + d[1]) * d[2] + d[0] * d[1];
if constexpr (N == 2) return d[0] + d[1];
return static_cast<T>(0.);
}

BVH_ALWAYS_INLINE static constexpr BBox make_empty() {
return BBox(
Vec<T, N>(+std::numeric_limits<T>::max()),
Vec<T, N>(-std::numeric_limits<T>::max()));
}
Vec<T, N> min, max;

BBox() = default;
BVH_ALWAYS_INLINE BBox(const Vec<T, N> &vmin, const Vec<T, N> &vmax) : min(vmin), max(vmax) {}
BVH_ALWAYS_INLINE explicit BBox(const Vec<T, N> &point) : BBox(point, point) {}

BVH_ALWAYS_INLINE BBox &extend(const Vec<T, N> &point) { return extend(BBox(point)); }

BVH_ALWAYS_INLINE BBox &extend(const BBox &other)
{
min = robust_min(min, other.min);
max = robust_max(max, other.max);
return *this;
}

BVH_ALWAYS_INLINE Vec<T, N> get_diagonal() const { return max - min; }
BVH_ALWAYS_INLINE Vec<T, N> get_center() const { return (max + min) * static_cast<T>(0.5); }

BVH_ALWAYS_INLINE T get_half_area() const
{
auto d = get_diagonal();
static_assert(N == 2 || N == 3);
if constexpr (N == 3)
return (d[0] + d[1]) * d[2] + d[0] * d[1];
if constexpr (N == 2)
return d[0] + d[1];
return static_cast<T>(0.);
}

BVH_ALWAYS_INLINE static constexpr BBox make_empty()
{
return BBox(Vec<T, N>(+std::numeric_limits<T>::max()), Vec<T, N>(-std::numeric_limits<T>::max()));
}
};

} // namespace bvh::v2
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