64-bits of Glorious Light An Introduction to HDRR CSE3AGT - Paul Taylor 2010

HDRR vs LDRR ons/1/1d/Farcryhdr.jpg

We are going to look at Colour a little differently... Red Green Blue Luminosity Chromaticity r and b

Luminosity eincolour.com/tutorial s/color-space- conversion.htm

CIELUV and CIEXYZ L u v – L is the Luminance – u and v are the Chromaticity X Y Z ( also known as tristimulus values) These are the amounts of each of the primaries needed for an observer to see the desired colour Y is the Luminance Normalised it becomes CIExyz x = X / (X + Y + Z) y = Y / (X + Y + Z) z = Z / (X + Y + Z) = 1 - (x + y)

tes/products/documentatio n/hpc/ipp/ippi/ippi_ch6/ch 6_color_models.html

An XYZ graph

Why are we going to do this?

RGB and sRGB RGB is Gamma independant Range [0,1] sRGB utilises a Gamma of 2.2 and a D65 Whitepoint

Colour Format Factors Lab Gamut Efficiency -% of visible colours represented Coding Efficiency -% of data space that represents real colours (waste)

The Lab Gamut

RGB Colour Spaces l#Specifications

Adobe RGB

sRGB

NTSC RGB

PAL / SECAM RGB

sRGB to XYZ n_RGB_XYZ_Matrix.html#WSMatrices sRGB->XYZXYZ->sRGB

XYZ to Luv D65 = X r =95.04, Y r =100.00, Z r = dex.html?Eqn_RGB_XYZ_Matrix.htm l#WSMatrices

Luminance Light of an equal power, but different wavelength does not appear equally bright to the viewing eye.

Chromaticity Chromaticity r and g from a CIE RGB source: ce

U’ and v’

lnikon/light/chap03/sec01.htm

Why are we doing this?

HDRR vs LDRR ons/1/1d/Farcryhdr.jpg

HDRR vs LDRR ons/1/1d/Farcryhdr.jpg

Y Cb Cr (YCC) What is it? – A Colour Format yes – Y is the luma – Chroma Blue – Chroma Red Y’CbCr has a non-linear luma (Gamma encoded)

CIE Chromacity Diagram

Using all this to create HDRR

Emulating Light Our Contrast adaption is an adjustment of the iris, a relatively slow chemical change Dynamic Contrast of the eye is 1,000,000 : 1 Static Contrast of the sys is 10,000 : 1

Light Blooming When Light scatters in the Lens of your Eye The brain interprets this as a bright spot. – This has the effect of really bright stuff bleeding over the edges of other objects. Emulating this bleeding makes the player think the white spot is insanely bright!

Lens Flare This is the diffraction of light in the lens of your eye It results in rays of light emanating from small light sources, and possible chromatic effects. We have been emulating this effect for a long time, but with HDRR can also include the bleeding / distortion in relating to world objects

Screen Effects (Not all HDRR) Depth blur (Near and Far) Motion Blur Full Screen Bloom Material Bloom Cross fading (Cinematic) Screen Distortions (Various) – Heat Haze – Colour Filters (Night Vision) HDRR effects!!

Tone Mapping This is us trying to jam 1,000,000 : 1 contrast ratio onto a screen which may have only 5,000 : 1 ratio.

Luv / XYZ benefits Light Mixing Two lights A and B All possible outputs lie directly between the two points

LogLuv Encoding LogLuv is a great format for punching down the size of LUV encoded data into variables such as Int8’s or similar smaller data sizes

HDR Teapot

References t=28 t=28 ull_screen_effect ull_screen_effect gh_dynamic_range_rendering gh_dynamic_range_rendering