Structs: Struct Type Reference

Struct types the LCC4UnrealRuntime module exposes.

#include "Core/LCCStructure.h"

Structs marked BlueprintType can be split and assembled in Blueprint with Break / Make nodes.

Performance

FRenderInfo

Common performance parameters. Used by ULCCComponentBase::Performance.

The design characteristic of this struct is that every value comes with an enable checkbox. While the checkbox is off the built-in plugin default is used, and the entered value only applies once it is on. The matching Setter on the Component sets the checkbox to true automatically.

Helper methods:

bool HasMaxDistanceLimit() const;      // whether a distance limit exists
bool HasMaxNumLimit() const;           // whether a count limit exists
bool NeedPreload() const;              // whether preloading is needed
uint32 GetMaxDistance() const;         // effective maximum distance
uint32 GetMaxSplatNum() const;         // effective maximum count
float GetLevelFactor() const;          // effective LOD factor
uint32 GetStartLevel() const;          // effective start Level
uint32 GetEndLevel() const;            // effective end Level
uint32 GetMaxCollisionDistance() const;
uint32 GetPreloadDistance() const;     // returns GetMaxDistance() + 35
bool GetIfUseFullLoad(uint32 SplatNum) const;   // whether the given count uses full load
void Reset();                          // resets the value fields only, not the enable checkboxes

Two easy pitfalls:

• Reset() resets the value fields only (distance, count, Level, factor) and resets none of the b* enable checkboxes, nor bUseFullLoad and FullLoadSplatNum.
• FRenderInfo::GetPreloadDistance() returns GetMaxDistance() + 35, while the function of the same name on the component, ULCCComponentBase::GetPreloadDistance(), returns the raw field value. The two results differ.

The Getters return the effective value: while the checkbox is off they return the built-in default, not the value entered earlier. This is easy to confuse, and reading the field directly may differ from calling the Getter.

Usage notes:

• Modifying through the Setter on the Component is the easiest route and needs no manual checkbox handling.
• When changing struct fields directly, remember to set the checkbox to true as well, otherwise nothing takes effect.

// recommended: use the Setter, the checkbox is handled automatically
Component->SetMaxDistance(200);

// changing the field directly requires setting the checkbox yourself
Component->Performance.bDistanceLimit = true;
Component->Performance.MaxDistance = 200;

FLCCRenderInfo

LCC1-specific performance parameters. Used by ULCCComponent::LCCPerformance.

Helper methods:

float GetSortFactor() const;
bool GetIfAddExtraPreNodes() const;
void Reset();

Related page: ULCCComponent

Metadata

FMetaInfoBase

Metadata base struct, inherited by both FLCCMetaInfo and FLCC2MetaInfo. Return type of ULCCComponentBase::GetMetaInfo.

Helper methods:

bool IsValid() const;              // whether the metadata is valid
void Reset();
bool IsRTK() const;                // whether RTK geographic information is present
FVector GetOffset() const;         // offset as FVector, returns a zero vector with a warning when fewer than 3 elements
FVector3f GetScale();              // note: not const, and does not check the element count
EFileType GetFileType() const;     // file type enum
float GetVersion() const;          // version as float
uint32 GetLevel0SplatNum() const;  // splat count of Level 0, in units of ten thousand

GetScale() and GetOffset() differ in robustness: GetOffset() checks the element count and returns a zero vector with a warning when there are fewer than 3, while GetScale() indexes the first three elements directly and goes out of bounds when Scale has fewer than 3 elements.

IsRTK() decides by Epsg > 0 plus a non-zero offset and looks at the data only. It is not equivalent to CanUseGeoPlace(), which additionally requires bEnableGeoPlace to be enabled and the geo referencing system to be created.

Usage notes:

• Read it after loading completes; the fields are all zero values while the data is not ready.
• TotalSplats is the total amount of the data. ULCCComponentBase::GetSplatNumber() returns this very field, so the two are the same value.

if (Component->CheckIfLoaded())
{
    const FMetaInfoBase Meta = Component->GetMetaInfo();

    UE_LOG(LogTemp, Log, TEXT("Name: %s"), *Meta.Name);
    UE_LOG(LogTemp, Log, TEXT("Levels: %d, total splats: %d"),
        Meta.TotalLevel, Meta.TotalSplats);
    UE_LOG(LogTemp, Log, TEXT("Level 0 splats: %u (ten thousand)"),
        Meta.GetLevel0SplatNum());
    UE_LOG(LogTemp, Log, TEXT("Has SH: %s"),
        Meta.GetFileType() == EFileType::Quality ? TEXT("yes") : TEXT("no"));

    if (Meta.IsRTK())
    {
        UE_LOG(LogTemp, Log, TEXT("EPSG: %d, offset: %s"),
            Meta.Epsg, *Meta.GetOffset().ToString());
    }
}

Blueprint as text:

[Get Meta Info]
        Target = (LCC Component)
        │ Return Value ──┐
        ▼                │
[Break FMetaInfoBase] ◀──┘
        Name → [Print String]
        Total Splats → [Print String]
        Total Level → [Print String]

FLCCMetaInfo

Complete LCC1 metadata, inheriting FMetaInfoBase.

The condition of IsValid() is stricter than in the base class: TotalLevel, TotalSplats, CellLengthX, CellLengthY, and IndexDataSize must all be greater than 0.

Bounding box methods (all returning FBox, C++ only):

FVector2f GetCellLength() const;
int32 GetXNum() const;                    // grid count along X
int32 GetYNum() const;                    // grid count along Y
FBox GetVisibleBoundingBox() const;       // visible bounding box
FBox GetScaleBox() const;
FBox GetEnvironmentScaleBox() const;
FBox GetEnvironmentVisibleBox() const;
FBox GetShcoef() const;                   // value range of the spherical harmonics
FBox GetEnvShcoef() const;
FBox GetNormal() const;
FBox GetEnvNormal() const;
FBox GetColor() const;
FVector2f GetOpacity() const;

FLCC2MetaInfo

Complete LCC2 metadata, inheriting FMetaInfoBase. Return type of ULCC2Component::GetMetaInfo2.

The condition of IsValid() is that Files is not empty.

Helper method:

FBox GetBounds() const;    // bounding box of the root node, already converted to centimeters

About SHBands: it decides the stride of the spherical harmonics slots, so every data source inside the same spherical harmonics buffer has to agree. A tree mixing different band counts takes the widest one. Single-file formats (.sog / .spz / .ply) read the exact band count from the decoder header; LCC2 has no per-file band concept and FileType decides it, with Portable having no spherical harmonics and Quality having 3 bands.

Raycast Result

FLCCSplat

Hit result of a ray test. Used by the ray test functions of ULCCComponent.

FLCCSplat Hit;
if (LineTraceSingle(Start, End, Hit, false, 0.f, 0.f))
{
    // hit position
    const FVector HitPos = Hit.Location;
    // detail level currently loaded at that spot
    const int32 Level = Hit.NodeVector.Level;
}

Related page: ULCCComponent ray tests

FLCCVector

Node coordinates, locating a node in the octree.

The parameterized constructor and the copy constructor clamp the three fields to non-negative values, but a direct assignment (writing the fields after default construction, or using operator=) does not clamp.

Helper methods:

FString ToString() const;     // format is "X:%i,Y:%i,Level:%i"
void Reset();
static double Dist2D(const FLCCVector& A, const FLCCVector& B);

Equality compares X, Y, and Level only, not the internal camera information and other runtime fields.

Level tells whether the data currently visible is fine or coarse; a smaller value is finer.

Bounding Box

FBoundingBoxInfo

Bounding box information.

FBoundingBoxInfoWithName

Named bounding box, used by the attribute list in the metadata.

Equality compares Name only.

SOG Metadata

This group of structs describes the metadata of a .sog file and is output by the SOG parsing functions of ULCCUtilLibrary.

FLCC2SogMeta

Main SOG metadata struct.

Helper method:

bool HasShN() const;    // whether high-order spherical harmonics are present, equivalent to ShN.Files being non-empty

Usage notes:

• Read it with ParseSogMetaFromFile without loading the render data, at very low cost.
• It reveals the point count and the spherical harmonics situation before loading, so the quality configuration can be decided in advance.

FLCC2SogMeta Meta;
if (ULCCUtilLibrary::ParseSogMetaFromFile(Path, Meta))
{
    UE_LOG(LogTemp, Log, TEXT("Version: %d, count: %d, high-order SH: %s"),
        Meta.Version, Meta.Count, Meta.HasShN() ? TEXT("yes") : TEXT("no"));
}

FLCC2SogShN

High-order spherical harmonics data.

Helper method: bool HasShN() const.

FLCC2SogImageData

SOG image data.

Other Sub-structs

The following structs contain only a file list, some with a quantization codebook:

Codebook is a TStaticArray<float, 256>, not a UPROPERTY, and is not visible in Blueprint.

Octree Nodes

This group of structs describes the LCC2 octree. It is low-level data that regular development does not need to touch directly.

FTreeNode

Octree node.

Helper method:

void ClearIterative();

It collects every node breadth-first and cleans up in reverse order, avoiding a stack overflow from recursive destruction in a very deep tree. Call it before an FTreeNode held manually leaves scope.

FTreeNodeData

Node data container, marking with booleans whether each kind of data is present.

FTreeNodeData3DGS

FTreeNodeDataMesh

FTreeNodeDataBVH

See Also

• ULCCComponentBase: usage of FRenderInfo and FMetaInfoBase
• ULCCComponent: usage of FLCCSplat and FLCCRenderInfo
• ULCCUtilLibrary: the SOG metadata parsing functions
• Enums: the enum types used in these structs