FVirtualTextureTileOffsetData Struct Reference

#include <VirtualTextureBuiltData.h>

Public Member Functions
uint32	GetTileOffset (uint32 InAddress) const

Public Attributes
uint32	Width = 0
uint32	Height = 0
uint32	MaxAddress = 0
TArray< uint32 >	Addresses
TArray< uint32 >	Offsets

Friends
FArchive &	operator<< (FArchive &Ar, FVirtualTextureTileOffsetData &TileOffsetData)

Detailed Description

Compact structure to find tile offsets within a sparse chunk. The tiles are stored in Morton order inside the chunks. But for UDIM textures some areas of a mip level may be empty and so some tiles don't exist. We could store one chunk offset per tile, but that uses a large amount of memory. So we need a fast, but memory efficient way to get from tile index to chunk location. This structure splits the space into contiguous blocks of empty or non-empty tiles. If a block is non-empty it has an offset into the chunk, and if it is empty it has a special "empty" offset. Within a non-empty block, all tiles exist and are contiguous. Because the tiles are in Morton order and UDIMs are aligned on power of 2 boundaries the sequences are not usually very fragmented, so textures can be described with a low number of blocks. Lookup of tile index is done at the cost of a binary search of Morton address through the stored block addresses.

Member Function Documentation

GetTileOffset()

uint32 FVirtualTextureTileOffsetData::GetTileOffset

(

uint32

InAddress

)

const

Call at runtime to get the final tile offset in the chunk.

Friends And Related Symbol Documentation

operator<<

FArchive & operator<< ( FArchive &  Ar, FVirtualTextureTileOffsetData &  TileOffsetData  )

friend

Serialization helper.

Member Data Documentation

Addresses

TArray<uint32> FVirtualTextureTileOffsetData::Addresses

Sorted list of contiguous tile block addresses.

Height

uint32 FVirtualTextureTileOffsetData::Height = 0

MaxAddress

uint32 FVirtualTextureTileOffsetData::MaxAddress = 0

Upper bound Morton address for managed area.

Offsets

TArray<uint32> FVirtualTextureTileOffsetData::Offsets

Offset for each block in Addresses. An empty block is marked with ~0u.

Width

uint32 FVirtualTextureTileOffsetData::Width = 0

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The documentation for this struct was generated from the following files:

• Engine/Source/Runtime/Engine/Private/VT/VirtualTextureBuiltData.h
• Engine/Source/Runtime/Engine/Private/VT/VirtualTextureBuiltData.cpp