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LuxRender Textures Spectrum
The color of a light source or object depends on the wavelength of the light, or the combination of wavelengths at which a light source emits light. Although most light sources emit light at a continuous range of frequencies and our eyes are sensitive to a number of different frequencies, we still perceive the light as if it had a single frequency. This means multiple different spectral characteristics can result in the same color sensation.
When light sources illuminate surfaces, the resulting perceived color depends on the spectral distribution of both the light source and the surface. Because spectral characteristics can not be represented in an RGB image, LuxRender provides a number of additional ways to specify the spectrum of light sources.
By indicating a color temperature, LuxRender will use the spectral distribution of a Blackbody. This is useful for for example light bulbs (2800-3300K), candles (1850K) and the sun (5000-6500K).
A range of color temperatures. The middle lamp has a color temperature of 6500K.
This experimental spectrum uses a sine wave. Its practical use is limited.
This experimental spectrum uses a sine wave. Its practical use is limited.
The Gaussian spectrum uses a Gaussian distribution. It is defined by a frequency (in nanometers) and the standard deviation of the bell curve. The latter controls the width of the curve; low values result in saturated colors while higher values result in less saturated tones. There is also an "energy" value which will determine how much of the incoming energy is reflected/transmitted/emitted.
So in a sense, this is a fancy HSV color selector, where wavelength = hue, width = saturation, and energy = value. The Gaussian texture is generally the most useful spectrum texture for defining arbitrary light colors.
Lamps emitting light around 589nm, with increasingly wide spectrum.
Color depth, also known as color at depth, is a texture designed to make setting absorption simpler. Normally, you set absorption by defining the color that will be absorbed, resulting in a color control that is essentially "backwards". This texture allows you to instead set the desired result color and how far the light should penetrate before reaching that color.
Parameters
- Transmission color - The target color of the transmitted light as it reaches the defined depth.
- Depth - The depth at which the specified transmission color is reached.
This generates a spectrum using numerical data as input. A frequency range should be provided plus a number of values for emissions at regular frequency intervals within that range.
This generates a spectrum using numerical data as input. A set of wavelengths and their respective emission power should be provided.
Lampspectrum uses presets to load measured spectral data for various kinds of lamps.
The whole set of Lampspectra.
The color stripes are taken from the Gaussian wavelength (left to right): 380, 414, 448, 482, 516, 550, 584, 618, 652 and 686.
Natural Daylight.
Paraffin Candle Flame.
SOX Low Pressure Sodium Discharge Lamp.
Regular High Brightness Blue LED.
Sylvania [G8T5 8W] Germicidal Lamp.