# Tag Info

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The choice of various tristimulus color spaces or spectral rendering matters when you're doing multiplicative color operations, like multiplying a light source color by a material reflectance. For these operations, the spectral approach is most accurate, and multiplying tristimulus color values is a pretty coarse approximation (and also depends a lot on the ...

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Just turning the comments into a fully-fledged answer as it may prove useful to others. IMHO, the alpha channel should always be linear and treated as such. You described blending a black quad over a white background using alpha=0.95, and mapping the result back to non-linear space. We'd expect a resulting, physical intensity value of 0.05. If the non-...

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How do I calculate average hue, since the numbers loop around? I will get silly answers sometimes. For example, in HSB/HSL, the average of hue=10 (slightly orange red) and hue=350 (slightly blue red) would arithmetically be hue=(10+350)/2=180 (cyan). How to calculate mean and standard deviation for hue values from 0 to 360? and Averaging circular values (...

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How accurate it is to estimate rendering equation using wavelengths This is probably as accurate as it gets if you are using with the full form of Fresnel equation. then convert result to CIE XYZ This brings in two problems with respect to accuracy. If the spectral distribution of your illuminant is different from the one that is used by CIE, you would ...

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This effect is called Color Cycling (or Palette Shifting). Mark Ferrari has a great GDC talk where he demonstrates and explains the entire technique. You can view a bunch of his artwork based on this technique here. The main idea is that each pixel is painted not with a single color, but as values of a look-up table to a palette of colors. The entire image ...

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I fully understand the confusion (I was also a bit confused when I saw it). So, I decided to look at the ACES implementation of the ST 2084 EOTF. https://github.com/ampas/aces-dev/blob/v1.0.3/transforms/ctl/lib/ACESlib.Utilities_Color.ctl#L402 From there it is very clear: You perform the transfer function on the R, G and B values separately and not by first ...

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Correct, the missing curvy section in the green-cyan-blue area represents where the red component would have to go negative to express those colors in CIE RGB coordinates. RGB and XYZ are, at one level, just different coordinate systems covering the same color space—the space of all colors visible to typical human vision. In a mathematical sense, when used ...

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The real story here is actually very interesting and can be enlightening. So I offer this alternate answer to help better answer this question. Also, my answer below is a very specific to this question. The full story is too big to put here, but worth the trouble of learning. In the 1930-50's researchers started looking into the human visual system. These ...

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Several reasons. Im listing them in random order There are entire industries that do other things than display things on computer screens. If you were to print a booklet, make a package, movie projection or paint a car you would probably be wise to be able to mathematically model it for design, quality control and documentation purposes. Not all screen ...

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The discrepancy comes from chromatic adaptation, which is included in the matrix from shadertoy. If you combine XYZ->AP1 with D65->D60 from the aces page you end up with the same matrix that I got by chaining XYZ->sRGB and sRGB->AP1 (with chromatic adaptation) together.

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