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64-bits of Glorious Light An Introduction to HDRR

64-bits of Glorious Light An Introduction to HDRR. CSE3AGR - Paul Taylor 2009. HDRR vs LDRR. http://upload.wikimedia.org/wikipedia/commons/1/1d/Farcryhdr.jpg. We are going to look at Colour a little differently. Red Green Blue Luminosity Chromaticity r and b. Luminosity.

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64-bits of Glorious Light An Introduction to HDRR

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  1. 64-bits of Glorious LightAn Introduction to HDRR CSE3AGR - Paul Taylor 2009

  2. HDRR vs LDRR • http://upload.wikimedia.org/wikipedia/commons/1/1d/Farcryhdr.jpg

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

  4. Luminosity • http://www.cambridgeincolour.com/tutorials/color-space-conversion.htm

  5. 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)

  6. An XYZ graph

  7. Why are we going to do this? • http://en.wikipedia.org/wiki/YCbCr

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

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

  10. The Lab Gamut

  11. RGB Colour Spaces • http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#Specifications

  12. Adobe RGB

  13. sRGB

  14. NTSC RGB

  15. PAL / SECAM RGB

  16. sRGB to XYZ http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html#WSMatrices sRGB->XYZ XYZ->sRGB

  17. XYZ to Luv D65 = Xr=95.04, Yr=100.00, Zr=108.88 http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html#WSMatrices

  18. Luminance • http://colorusage.arc.nasa.gov/lum_and_chrom.php Light of an equal power, but different wavelength does not appear equally bright to the viewing eye.

  19. Chromaticity • Chromaticity r and g from a CIE RGB source: http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition_of_the_CIE_XYZ_color_space

  20. U’ and v’

  21. http://www.nikon.com/about/feelnikon/light/chap03/sec01.htm

  22. Why are we doing this? • http://en.wikipedia.org/wiki/YCbCr

  23. HDRR vs LDRR • http://upload.wikimedia.org/wikipedia/commons/1/1d/Farcryhdr.jpg

  24. HDRR vs LDRR • http://upload.wikimedia.org/wikipedia/commons/1/1d/Farcryhdr.jpg

  25. 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)

  26. http://en.wikipedia.org/wiki/YCbCr

  27. CIE Chromacity Diagram • http://en.wikipedia.org/wiki/File:CIExy1931.svg

  28. Using all this to create HDRR

  29. 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

  30. 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!

  31. 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

  32. 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!!

  33. 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.

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

  35. 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

  36. HDR Teapot

  37. References • http://www.xnainfo.com/content.php?content=28 • http://www.absoluteastronomy.com/topics/Full_screen_effect • http://www.absoluteastronomy.com/topics/High_dynamic_range_rendering

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