Pxlink: Color Obsidian: [[DTA]] [[21-01-01-Pipes|Pipes]] [[13-01-01-Houdini|HOU Config]] [[11-01-01-Math|Math]] [[08-01-01-Material|Mat]]

Resolutions

Napkin math res

1024^2

1 048 576 pixels

4096^2

16 777 216 16 mil pixels = … mb
4096^2 pix = 33 550 points - 500 frames (~16 sek)
4k normal map at 80% UV usage can contain normal data from ~13.5m triangles at a density of one triangle per pixel.

Lidar - geotif file points 1 per meter is highest you will find

Color space Conversion

sRGB - on monitor looks like even distribution but is not / math in sRGB is not working
linear - look vanished
19% of light intensity is perceived by us as half . (and 50% of sRGB is 21% linear so after gamma applied is appealing and natural for eye)

sRGB

mid gray in middle (perceptual display of blacks) sRGB - 2.2 Gamma (1/2.2=0.4545)

Because our eyes is more sensitive to differences in darker colors than brighter, the darker parts gets more room in the small 0-255 value space.

For Color / Albedo

Linear RGB

image is brighter (black are crushed into small range)
Linear space value (0.5) converted to a gamma space rgb value: 0.5^(1 / 2.2) = ~0.73 * 255 = 186

In linear the brighter values are as important as the dark ones.

Quality of 16-bit linear is about equal to 12-bit sRGB.
Mid grey 18% after gamma look like 50%
For math, to get linear dependencies along gradient

sRGB to Liner Gamma To Linear

255 * POWER(gammavalue / 255,2.2)

if (sRGB <= 0.04045) 
  { 
  linearRGB = sRGB / 12.92; 
  } 
else 
  { 
  linearRGB = pow((sRGB + 0.055) / 1.055, gamma);
  }

Linear to sRGB Linear to Gamma

255*POWER(linearvalue/255,1/2.2)
pow(@linear, 0.4545);

pow (x, 0.4545) is a bit cheaper ‘cause there’s no division involved. 1/2.2 is 0.45

if (linearRGB <= 0.0031308) 
  { 
  sRGB = 12.92 * linearRGB; 
  } 
else 
  {
  sRGB = 1.055 * pow(linearRGB, 1.0 / gamma) - 0.055; 
  }

https://www.vfxwizard.com/tutorials/gamma-correction-for-linear-workflow.html

Quality

bpc – bit per channel
pbi - bits per image

Bit depth - The number of bits per pixel, sample, or texel in a bitmap image (holding one or mode image channels)

8 bit - what monitor can show
16bit - enough

bits per pixel	bits per channel	colors
1-bit color	1x2 binary	(2 colors)
8 bit	1x256	256 colors
16-bit	1x65k	1x65k colors	High color
24-bit	3x8 bpc = 256	16M colors	True color `LDR` (The human eye can discriminate up to ten million colors)
32-bit	4x8 bpc	16M colors	True color with Alpha RGBA
48 bit	3x16 bpc			RAW
96 bit	3x32 bpc		`HDR`

Formats

Formats meant for view or transports data.

exr - fastest save, saved as linear - less compression - multi layer

EXR with zip « LOSE LESS: Standard 32 bit . largest file nothing lost. perfect replication < hdri , cryptomats and sometimes displacement
EXR with DWAA - loose precision of highlight < smaller faster and can contain many images.

	usecase
`*.exr`	Render !!!	OpenEXR is Light & Magic high dynamic range raster file and floating-point precision. DJI Viewer. 32 bit files. EXR also has fast multi-threaded file reading and writing, leading to better read-write performance compared to other formats.
`*.tga`	Unreal (No windows prev!)	lossless Truevision Advanced 32-bit true color; that is, 24-bit (8 bpc) color plus an alpha channel,
`*.png`	Network	Portable Grap Network Graphic (48 bpi = 16 bit per channel bpc) PNG compression format is prone to white fringing and iffy alpha values in general when converted to Unreal engine formats.
`*.tif`	Print	loseless Adobe Tagged Image File Format, 8 or 16 bpc (to 48bit transp can constain metadata like GeoTiff) (LZW lossless compression)
`*.sbs`		Substance Designer Document
`*.sbsar`		Substance Archive
`*.iff`		maya “z-depth”

*.obj - no vertex color and 2-uvs standardized, no attribs
*.fbx -
*.gltf- Create an unwanted catalog in UE4, no Vert Color?
*.bgeo.sc - cache
*.sim - more expensive H cache (eg in output node in dop)

Aspect Ratio

4:3 1.33 - Old TV
16:9 1.77 - HDTV format (4:3 squared)

1920 x 1080 - full HD 1080p
2560 x 1440 - HDTV
3840 x 2160 - 4K (4K UHD) (2160p)
7680 × 4320 - (8K UHD)
17280 × 4320 - (16K)

1.85 - Widescreen - slightly wider than 16:9
2:1 2 - Univisium - versitile and save
21:9 2.33 -
2.35 - CinemaScope -
2.76 - imax

3440 x 1440 2.38:1 personal
4096 × 2160 1.89:1 4K (DCI) movie ind

Video formats

m4v < mp4 locked mkv < can have anything and support for corupted files

mov - edit on the file