Probe Class Reference

A probe can be used to capture the appareance of a scene at a given location as a 360° cubemap. More...

#include <Probe.hpp>

Public Member Functions
	Probe (LightProbe &probe, std::shared_ptr< Renderer > renderer, uint size, uint mips, const glm::vec2 &clippingPlanes)
void	update (uint budget)
uint	totalBudget () const
Probe &	operator= (const Probe &)=delete
	Probe (const Probe &)=delete
Probe &	operator= (Probe &&)=delete
	Probe (Probe &&)=delete
	~Probe ()=default

Static Public Member Functions
static void	extractIrradianceSHCoeffs (const Texture &cubemap, float clamp, std::vector< glm::vec3 > &shCoeffs)
	Decompose an existing cubemap irradiance onto the nine first elements of the spherical harmonic basis. More...

Private Types
enum class	ProbeState { DRAW_FACES , CONVOLVE_RADIANCE , GENERATE_IRRADIANCE }
	Probe update state machine. More...

Private Member Functions
void	convolveRadiance (float clamp, uint layer)
void	estimateIrradiance (float clamp)

Private Attributes
std::shared_ptr< Renderer >	_renderer
	The renderer to use.
Texture	_result
	The cubemap content.
Texture	_copy
	Downscaled copy of the cubemap content.
std::shared_ptr< Buffer >	_shCoeffs
	SH representation of the cubemap irradiance.
std::array< Camera, 6 >	_cameras
	Camera for each face.
glm::vec3	_position
	The probe location.
Program *	_radianceCompute
	Radiance preconvolution shader.
Program *	_irradianceCompute
	Irradiance SH projection shader.
ProbeState	_currentState = ProbeState::DRAW_FACES
	Current update state.
uint	_substepDraw = 0
	If drawing, current face.
uint	_substepRadiance = 1
	If convolving radiance, current level.

Detailed Description

A probe can be used to capture the appareance of a scene at a given location as a 360° cubemap.

This is often used to render realistic real-time reflections and global illumination effects. It is recommended to split the rendering, radiance precomputation for GGX shading and irradiance SH decomposition over multiple frames as those steps are costly.

Member Enumeration Documentation

ProbeState

enum class Probe::ProbeState

strongprivate

Probe update state machine.

Enumerator
DRAW_FACES	Drawing a cubemap face with the environment.
CONVOLVE_RADIANCE	Convolving the cubemap to generate radiance for a given roughness level.
GENERATE_IRRADIANCE	Integrate irradiance in a compute shader.

Constructor & Destructor Documentation

Probe() [1/3]

Probe::Probe	(	LightProbe &	probe,
		std::shared_ptr< Renderer >	renderer,
		uint	size,
		uint	mips,
		const glm::vec2 &	clippingPlanes
	)

Constructor

Parameters

probe	the probe in the scene
renderer	the renderer to use to fill the cubemap
size	the dimensions of the cubemap
mips	the number of mip levels of the cubemap
clippingPlanes	the near/far planes to use when rendering each face

Warning

If the renderer is using the output of the probe, be careful to not use the probe content in the last rendering step.

Probe() [2/3]

Probe::Probe ( const Probe &  )

delete

Copy constructor (disabled).

Probe() [3/3]

Probe::Probe ( Probe &&  )

delete

Move constructor (disabled).

~Probe()

Probe::~Probe ( )

default

Destructor

Member Function Documentation

convolveRadiance()

void Probe::convolveRadiance ( float  clamp, uint  layer  )

private

Perform BRDF pre-integration of the probe radiance for increasing roughness and store them in the mip levels.

Parameters

clamp	maximum intensity value, useful to avoid ringing artifacts
layer	first layer to process (in 1, mip count - 1)

estimateIrradiance()

void Probe::estimateIrradiance ( float  clamp )

private

Estimate the SH representation of the cubemap irradiance. The estimation is done on the GPU.

Parameters

clamp

maximum intensity value, useful to avoid temporal instabilities

extractIrradianceSHCoeffs()

void Probe::extractIrradianceSHCoeffs ( const Texture &  cubemap, float  clamp, std::vector< glm::vec3 > &  shCoeffs  )

static

Decompose an existing cubemap irradiance onto the nine first elements of the spherical harmonic basis.

Perform approximated convolution as described in Ramamoorthi, Ravi, and Pat Hanrahan. "An efficient representation for irradiance environment maps.", Proceedings of the 28th annual conference on Computer graphics and interactive techniques. ACM, 2001.

Parameters

cubemap	the cubemap to extract SH coefficients from
clamp	maximum intensity value, useful to avoid temporal instabilities
shCoeffs	will contain the irradiance SH representation

operator=() [1/2]

Probe & Probe::operator= ( const Probe &  )

delete

Copy assignment operator (disabled).

Returns

a reference to the object assigned to

operator=() [2/2]

Probe & Probe::operator= ( Probe &&  )

delete

Move assignment operator (disabled).

Returns

a reference to the object assigned to

totalBudget()

uint Probe::totalBudget

(

)

const

Returns

the total number of steps to completely update the probe data

update()

void Probe::update

(

uint

budget

)

Update the content of the probe and the corresponding radiance and irradiance.

Parameters

budget

the number of internal update steps to perform Each internal step (drawing a part of the environment, generating the convolved radiance, integrating the irradiance) has a given budget. Depending on the allocated budget, the probe will entirely update more or less fast.

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

• src/engine/renderers/Probe.hpp
• src/engine/renderers/Probe.cpp