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

#include <StelToneReproducer.hpp>

Public Member Functions
	StelToneReproducer ()
	Constructor.

virtual	~StelToneReproducer ()
	Desctructor.

void	setDisplayAdaptationLuminance (float displayAdaptationLuminance)
	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...

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 lumiances, 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...

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) const

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)

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

inline

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

inline

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 displayAdaptationLuminance )

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 )

inline

Parameters

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

◆ setInputScale()

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

Parameters

scale the global input scale

◆ setMaxDisplayLuminance()

void StelToneReproducer::setMaxDisplayLuminance ( float maxdL )

inline

Parameters

maxdL the maximum lumiance 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 )

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

Public Member Functions

Detailed Description

Member Function Documentation

◆ adaptLuminance()

◆ adaptLuminanceScaled()

◆ adaptLuminanceScaledLn()

◆ getDisplayGamma()

◆ getMaxDisplayLuminance()

◆ reverseAdaptLuminance()

◆ reverseAdaptLuminanceScaled()

◆ setDisplayAdaptationLuminance()

◆ setDisplayGamma()

◆ setInputScale()

◆ setMaxDisplayLuminance()

◆ setWorldAdaptationLuminance()

◆ xyYToRGB()