AZ::Render::ShadowmapAtlas Class Reference

#include <ShadowmapAtlas.h>

Classes
struct	Origin
struct	ShadowmapIndexNode

Public Member Functions
void	Initialize ()
	This initializes the packing of shadowmap sizes.
void	SetShadowmapSize (size_t index, ShadowmapSize size)
void	Finalize ()
uint16_t	GetArraySliceCount () const
ShadowmapSize	GetBaseShadowmapSize () const
Origin	GetOrigin (size_t index) const
Data::Instance< RPI::Buffer >	CreateShadowmapIndexTableBuffer (const AZStd::string &bufferName) const
const AZStd::vector< ShadowmapIndexNode > &	GetShadowmapIndexTable () const

Detailed Description

A shadowmap atlas is a single image array which contains shadowmaps with different sizes. This ShadowmapAtlas class determines the location of each shadowmap. This class also offers ShadowmapIndexTable, by which a compute shader can determine the corresponding shadowmap index from a coordinate (x, y, z) in the image array resource.

Member Function Documentation

CreateShadowmapIndexTableBuffer()

Data::Instance< RPI::Buffer > AZ::Render::ShadowmapAtlas::CreateShadowmapIndexTableBuffer

(

const AZStd::string &

bufferName

)

const

This returns a buffer by which a shader finds the shadowmap index in the atlas.

Parameters

bufferName

name of the buffer

Returns

buffer which a computer shader look up for the shadowmap index.

The buffer contains a table ShadowmapIndexTable which consists of "subtables." A subtable is an array of ShadowmapIndexNodes, and corresponds to a shadowmap Location. A ShadowmapIndexNode offers either the offset to another subtable or ths shadowmap index. So a subtable offers the offsets of the sub-subtable and shadowmap indices for direct children Location of the corresponding Location. We call the subtable for Locaion [] (the empty array) by "root subtable." The size of the root subtable equals to the array slice count of the image resource which the atlas occupies. The size of a non-root subtable (i.e., subtable for non-empty Location) is LocationIndexNum, i.e., 4. If m_nextTableOffset != 0, then m_nextTableOffset means the corresponding subtable's offset from the beginning of the buffer. If m_nextTableOffset == 0, then m_shadowmapIndex is the required shadowmap index.

For example, we assume baseShadowmapSize = 2048 light #0 uses Location [0], #1 does [1,0], and #2 does [1,1]. Then the resulting array "table" of T has size 6 and would be like below:

(root subtable, i.e., subtable for Location []) table[0] : m_nextTableOffset == 0, and m_shadowmapIndex == 0 the Location of the shadowmap is [0]. table[1] : m_nextTableOffset == 2 which indicate slice #1 is shared by multiple shadowmaps and the next subtable begin with offset 2.

(subtalble for Location [1]) table[2 + 0] : m_nextTableOffset == 0 and m_shadowmapIndex == 1 the Location of the shadowmap is [1, 0]. table[2 + 1] : m_nextTableOffset == 0 and m_shadowmapIndex == 2 the Location of the shadowmap is [1, 1]. table[4], table[5] : not used. For the way to extract shadowmap specific parameter, refer ShadowmapAtlasLib.azsli.

Finalize()

void AZ::Render::ShadowmapAtlas::Finalize

(

)

This decides shadowmap locations in the atlas. As we describe below (above of definition of Location), a location is encoded in a finite sequence of non-negative integers. This determines the locations from the largest shadowmaps to smaller ones, and the locations of the same size are occupied in the lexicographical order, e.g., [0,1,1] is occupied before [0,1,2].

GetArraySliceCount()

uint16_t AZ::Render::ShadowmapAtlas::GetArraySliceCount

(

)

const

This returns array slice count of the atlas. This has to be called after execution of Finalize().

Returns

array slice count of the atlas.

GetBaseShadowmapSize()

ShadowmapSize AZ::Render::ShadowmapAtlas::GetBaseShadowmapSize

(

)

const

This returns image size of the atlas. This has to be called after execution of Finalize().

Returns

image size of the atlas.

GetOrigin()

Origin AZ::Render::ShadowmapAtlas::GetOrigin

(

size_t

index

)

const

This returns shadowmap origin in the atlas. This has to be called after execution of Finalize().

Parameters

index

shadowmap index.

Returns

shadowmap origin in the atlas.

SetShadowmapSize()

void AZ::Render::ShadowmapAtlas::SetShadowmapSize	(	size_t	index,
		ShadowmapSize	size
	)

This sets shadowmap size.

Parameters

index	light index of shadowmap.
size	shadowmap size (width/height).

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The documentation for this class was generated from the following file:

• Gems/Atom/Feature/Common/Code/Source/CoreLights/ShadowmapAtlas.h