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27 votes

Are there common materials that aren't represented well by RGB?

There are various different types of limitation to take into consideration. Effects for which the path of a ray is dependent on its wavelength These are a class of effects for which spectral ...
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23 votes
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Why do red, green, and blue make up all the colors?

Let's reminds ourselves what light is. Radio waves, micro waves, X rays and gamma rays are all electromagnetic radiation and they only differ by their frequency. It just so happens that the human eye ...
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20 votes

Why do red, green, and blue make up all the colors?

They don't. The problem with the diagrams representing the visible and RGB gamuts is that they're presented on RGB displays. They obviously cannot show you what they cannot show you : the area inside ...
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17 votes

Why do red, green, and blue make up all the colors?

Humans are trichromatic, which means we have 3 different kinds of color receptors (better known as cone cells), each sensitive to a different set of wavelengths: Image source: wikipedia So it only ...
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16 votes

Are there common materials that aren't represented well by RGB?

I believe the most prominent spectral effect that can't be faithfully reproduced with RGB is dispersion, caused by dielectrics with spectrally varying index of refraction (usually modelled with the ...
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16 votes
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Is gamma still important to take into account?

Yes, while many screens and OS operations are using a gamma of 2.2 your hardware and computation result still need to be corrected. There are also special mediums such as broadcast TV's that have a ...
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13 votes
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For shader math, why should linear RGB keep the gamut of sRGB?

Talking about Linear RGB must be avoided because it does not tell you anything about the RGB colourspace intrinsics, i.e., Primaries, Whitepoint and Colour Component Transfer Functions. A few years ...
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11 votes
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What does "muted" mean in the context of color?

In terms of the HSV color space, "muted" colors are those with lower saturation and/or value. "Deep" colors are saturated but not too high in value (e.g. deep red) while colors with both high ...
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11 votes

Is gamma still important to take into account?

The de facto standard color space for digital images these days is sRGB. sRGB is a good default assumption if working with a display whose exact color space is not known (i.e. most random displays ...
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11 votes
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Why does checkerboard pattern on a computer screen appear with a yellowish tint?

Because your monitor is not properly calibrated. On my screen at home the top and bottom parts have the same hue. At my office though, the top part tends to looks a bit yellow compared to the bottom ...
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9 votes
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Actual vs Perceived Brightness of RGB Colour

Two different effects are causing the observation mentioned in the video. On one side, the vast majority of screens have a non linear response: if the RGB value is half as much, the emitted light ...
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9 votes

Why does the 1/r² term appear with point sources?

The concept of a point source is an approximation. Physically, light sources are extended objects and emit light from every point on their surface; but when you're far enough away (i.e. the distance ...
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8 votes
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What are the side effects of biasing brightness in continuous spectrum raytracing?

Generally, uniformly-weighted samples with a variable distribution (importance sampling) gives lower variance in the final average than uniformly-distributed samples with variable weights. This is a ...
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8 votes
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Understanding Jump Flooding Algorithm (JFA) for Voronoi Diagrams

I think that there is a bit of confusion in terminology. My understanding is that only the initially colored points, before step 1, are called seeds. Maybe this helps clarify the algorithm as well. ...
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7 votes

Spectral path tracing - image color/brightness incorrect

The problem lies mainly in CIE1931XYZ::tristimulusValues() function, where you normalize the resulting color to the luminance of your illuminant which causes that ...
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7 votes
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Function to convert HSV angle to RYB angle

I just discovered that Adobe color source includes HSV-RYB hue mapping functions (replicated in Ben Knight's Kuler-d3). Apparently Adobe uses uses piecewise linear gradients rather than the polynomial ...
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7 votes

Are there common materials that aren't represented well by RGB?

RGB works because that's how our sensory apparatus works. Ina addition to dispersion, some man made materials and insect bodies sometimes have surfaces that have very tight color bands. These might ...
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7 votes
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How much precision (half, float, double, etc) is enough for a Color class?

Colors shown on your display or saved to standard image file formats use 8 bits per component. So to store these colors it suffices to use four bytes (unsigned char)...
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7 votes
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What is the most physically accurate representation of color possible in computer graphics?

The most physically accurate way would be to have a $l(\theta)$ which for each possible color frequency has a certain value. Converting to RGB would then need a frequency responce function for each ...
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7 votes

What is the most physically accurate representation of color possible in computer graphics?

There is spectral rendering, where you can quantize the visible wavelengths from ~390nm to ~700nm to N discrete wavelengths instead of the standard 3 for RGB. Then if you had to model say a prism, you ...
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6 votes

Brightness and contrast VS Gamma, is it possible to identify the gamma "correction amount"?

If I get correctly what you are asking you basically just need to find the G in this equation: $$Image_{out} = Image_{in}^G$$ This could be easily solved as $$G = \frac{\log{Image_{out}}}{\log{...
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6 votes
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Is there a way to interpolate color across the line with only integer calculation ?`

Yes, it is possible to use only integer calculations. I will describe how, but bear in mind that the difference in speed between integer arithmetic and floating point arithmetic is not as great as it ...
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  • 5,902
6 votes

Why would a 4d texture be used for color conversion?

I think your quote refers to conversion between color spaces, rather than color grading. 4d textures could be used as lookup tables to convert color spaces like CMYK to some other space. Since CMYK ...
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  • 312
6 votes

How do you deal with clipping when rendering to a limited colorspace?

Effectively, before you start to think about clipping/clamping, you'll need a general approach to map the much wider color range you are working in onto the [0,1] triplets you want to output. There ...
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  • 266
5 votes
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What would be the correct way to calculate saturation in this case?

There is unfortunately no good answer to this question. Simply it wont work. There is no good way to define colorful, it this context. Cie is trying to capture the physical measurement. It however ...
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5 votes
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Is colorized subpixel rendering possible?

Here's an example of a downsampling filter that takes pixel geometry into account: Increasing image resolution on portable displays by subpixel rendering. Image (a) below is an image downsampled ...
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5 votes
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How to do a color separation with more than 3 primary colors

The mathematical approach to this is to represent the other colors/light sources in terms of your standard primaries in the color space. Represent your target color and available light sources as ...
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5 votes

Why does the 1/r² term appear with point sources?

It is the inverse square law of light for a pure point light. $E = \frac{I}{r^2}$ Where E is illuminance and I is pointance or power/flux per unit solid angle.
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5 votes
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Encode two R11G11B10F buffers into one using Y'CbCr?

You might want to look at The Compact YCoCg Framebuffer. It uses a 2-channel buffer to store luminance for every pixel and the two chroma components in half the pixels each, forming a checkerboard. It ...
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5 votes
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Calculate an equally bright grey to a linear RGB colour

The easiest way to get the perceived brightness of a color is to calculate the Luma. Finding the grey color with the same luma is easy - just set all of the RGB components to the desired luma value. ...
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