StelToneReproducer Class Reference

Converts tones in function of the eye adaptation to luminance. More...

#include <StelToneReproducer.hpp>

Public Slots
void	setDisplayAdaptationLuminance (float Lda)
	Set the eye adaptation luminance for the display (and precompute what can be) Usual luminance range is 1-100 cd/m^2 for a CRT screen. More...
float	getDisplayAdaptationLuminance () const
void	setWorldAdaptationLuminance (float worldAdaptationLuminance)
	Set the eye adaptation luminance for the world (and precompute what can be) More...
float	getWorldAdaptationLuminance () const
	Get the eye adaptation luminance for the world.
void	setInputScale (float scale=1.f)
	Set the global scale applied to input luminances, i.e before the adaptation It is the parameter to modify to simulate aperture*exposition time. More...
float	getInputScale () const
	Get the global scale applied to input luminances, i.e before the adaptation.
void	setMaxDisplayLuminance (float maxdL)
	Set the maximum luminance of the display (CRT, screen etc..) This value is used to scale the RGB range. More...
float	getMaxDisplayLuminance () const
	Get the previously set maximum luminance of the display (CRT, screen etc..) This value is used to scale the RGB range. More...
float	getDisplayGamma () const
	Get the display gamma. More...
void	setDisplayGamma (float gamma)
	Set the display gamma. More...
bool	getFlagUseTmGamma () const
void	setFlagUseTmGamma (bool b)
void	setFlagSRGB (bool val)
	Set whether to use an sRGB (default, true) or AdobeRGB color conversion matrix for the sky colors. More...
bool	getFlagSRGB () const

Signals
void	worldAdaptationLuminanceChanged (double)
void	displayAdaptationLuminanceChanged (double)
void	maxDisplayLuminanceChanged (double)
void	inputScaleChanged (double)
void	displayGammaChanged (double)
void	flagUseTmGammaChanged (bool)
void	flagSRGBChanged (bool val)

Public Member Functions
	StelToneReproducer ()
	Constructor.
virtual	~StelToneReproducer () Q_DECL_OVERRIDE
	Desctructor.
float	adaptLuminance (float worldLuminance) const
	Return adapted luminance from world to display. More...
float	reverseAdaptLuminance (float displayLuminance) const
	Return adapted luminance from display to world. More...
float	adaptLuminanceScaled (float worldLuminance) const
	Return adapted luminance from world to display with 1 corresponding to full display white. More...
float	reverseAdaptLuminanceScaled (float displayLuminance) const
	Return adapted luminance from display to world with 1 corresponding to full display white. More...
float	adaptLuminanceScaledLn (float lnWorldLuminance, float pFact=0.5f) const
	Return adapted ln(luminance) from world to display with 1 corresponding to full display white. More...
void	xyYToRGB (float *xyY) const
	Convert from xyY color system to RGB. More...
void	getShadersParams (float &a, float &b, float &c, float &d, bool &useGamma, bool &sRGB) const

Properties
double	worldAdaptationLuminance
double	displayAdaptationLuminance
double	maxDisplayLuminance
double	inputScale
double	displayGamma
bool	flagUseTmGamma
bool	flagSRGB

Detailed Description

The aim is to get on the screen something which is perceptualy accurate, ie. to compress high dynamic range luminance to CRT display range. The class perform mainly a fast implementation of the algorithm from the paper [1], with more accurate values from [2]. The blue shift formula is taken from [3] and combined with the Scotopic vision formula from [4].

Important : you may call setDisplayAdaptationLuminance() and setWorldAdaptationLuminance() before any call to xyYToRGB() or adaptLuminance otherwise the default values will be used. (they are appropriate for a daylight sky luminance)

The user can configure properties of the screen and environmant in the TonemappingDialog: displayAdaptationLuminance, maxDisplayLuminance and displayGamma. The latter is not fixed to the sRGB value of 2.2 but should probably also not deviate too much.

REFERENCES : Thanks to all the authors of the following papers I used for providing their work freely online.

[1] "Tone Reproduction for Realistic Images", Tumblin and Rushmeier, IEEE Computer Graphics & Application, November 1993

[2] "Tone Reproduction and Physically Based Spectral Rendering", Devlin, Chalmers, Wilkie and Purgathofer in EUROGRAPHICS 2002

[3] "Night Rendering", H. Wann Jensen, S. Premoze, P. Shirley, W.B. Thompson, J.A. Ferwerda, M.M. Stark

[4] "A Visibility Matching Tone Reproduction Operator for High Dynamic Range Scenes", G.W. Larson, H. Rushmeier, C. Piatko

Member Function Documentation

adaptLuminance()

float StelToneReproducer::adaptLuminance ( float  worldLuminance ) const

inline

Parameters

worldLuminance

the world luminance to convert in cd/m^2

Returns

the converted display luminance in cd/m^2

adaptLuminanceScaled()

float StelToneReproducer::adaptLuminanceScaled ( float  worldLuminance ) const

inline

Parameters

worldLuminance

the world luminance to convert in cd/m^2

Returns

the converted display luminance with 1 corresponding to full display white. The value can be more than 1 when saturated.

adaptLuminanceScaledLn()

float StelToneReproducer::adaptLuminanceScaledLn ( float  lnWorldLuminance, float  pFact = 0.5f  ) const

inline

Parameters

lnWorldLuminance	the world luminance to convert in ln(cd/m^2)
pFact	the power at which the result should be set. The default is 0.5 and therefore return the square root of the adapted luminance

Returns

the converted display set at the pFact power. Luminance with 1 corresponding to full display white. The value can be more than 1 when saturated.

getDisplayGamma

float StelToneReproducer::getDisplayGamma ( ) const

inlineslot

Returns

the display gamma. Default value is 2.2222 for a CRT, and sRGB LCD (and similar modern) panels try to reproduce that.

getMaxDisplayLuminance

float StelToneReproducer::getMaxDisplayLuminance ( ) const

inlineslot

Returns

the maximum display lumiance in cd/m^2. Typical default values for CRT is 120 cd/m^2, LCD panels often have more, which may have been adjusted previously by setMaxDisplayLuminance().

reverseAdaptLuminance()

float StelToneReproducer::reverseAdaptLuminance ( float  displayLuminance ) const

inline

Parameters

displayLuminance

the display luminance to convert in cd/m^2

Returns

the converted world luminance in cd/m^2

reverseAdaptLuminanceScaled()

float StelToneReproducer::reverseAdaptLuminanceScaled ( float  displayLuminance ) const

inline

Parameters

displayLuminance

the display luminance with 1 corresponding to full display white. The value can be more than 1 when saturated.

Returns

the converted world luminance in cd/m^2

setDisplayAdaptationLuminance

void StelToneReproducer::setDisplayAdaptationLuminance ( float  Lda )

slot

Parameters

displayAdaptationLuminance

the new display luminance in cd/m^2. The initial default value is 50 cd/m^2

setDisplayGamma

void StelToneReproducer::setDisplayGamma ( float  gamma )

slot

Parameters

gamma

the gamma. Initial default value is 2.2222 for a CRT, and sRGB LCD (and similar modern) panels try to reproduce that.

setFlagSRGB

void StelToneReproducer::setFlagSRGB ( bool  val )

slot

The actual matrix is in the xyYtoRGB.glsl shader program.

setInputScale

void StelToneReproducer::setInputScale ( float  scale = 1.f )

slot

Parameters

scale

the global input scale

setMaxDisplayLuminance

void StelToneReproducer::setMaxDisplayLuminance ( float  maxdL )

slot

Parameters

maxdL

the maximum luminance in cd/m^2. Initial default value is 100 cd/m^2. Higher values indicate "This display can faithfully reproduce brighter lights, therefore the sky will usually appear darker".

setWorldAdaptationLuminance

void StelToneReproducer::setWorldAdaptationLuminance ( float  worldAdaptationLuminance )

slot

Parameters

worldAdaptationLuminance

the new world luminance in cd/m^2. The initial default value is 40000 cd/m^2 for Skylight Star Light : 0.001 cd/m^2 Moon Light : 0.1 cd/m^2 Indoor Lighting : 100 cd/m^2 Sun Light : 100000 cd/m^2

xyYToRGB()

void StelToneReproducer::xyYToRGB

(

float *

xyY

)

const

The first two components x and y indicate the "color", the Y is luminance in cd/m^2.

Parameters

xyY	an array of 3 floats which are replaced by the converted RGB values