Spectral rendering
Encyclopedia
In computer graphics, spectral rendering is where a scene's light transport is modeled with real wavelengths. This process is typically a lot slower than traditional rendering, which renders the scene in its red, green, and blue components and then overlays the images. Spectral rendering is often used in ray tracing or photon mapping
to more accurately simulate the scene, often for comparison with an actual photograph to test the rendering algorithm (as in a Cornell Box
) or to simulate different portions of the electromagnetic spectrum
for the purpose of scientific work. The images simulated are not necessarily more realistic appearing; however, when compared to a real image pixel for pixel, the result is often much closer.
Spectral rendering can also simulate light sources and objects more effectively, as the light's emission spectrum
can be used to release photons at a particular wavelength in proportion to the spectrum. Objects' spectral reflectance curves can similarly be used to reflect certain portions of the spectrum more accurately.
As an example, certain properties of tomatoes make them appear differently under sunlight than under fluorescent light. Using the blackbody radiation equations to simulate sunlight or the emission spectrum of a fluorescent bulb in combination with the tomato's spectral reflectance curve, more accurate images of each scenario can be produced.
Photon mapping
In computer graphics, photon mapping is a two-pass global illumination algorithm developed by Henrik Wann Jensen that solves the rendering equation. Rays from the light source and rays from the camera are traced independently until some termination criterion is met, then they are connected in a...
to more accurately simulate the scene, often for comparison with an actual photograph to test the rendering algorithm (as in a Cornell Box
Cornell Box
The Cornell Box is a test aimed at determining the accuracy of rendering software by comparing the rendered scene with an actual photograph of the same scene. It was created by Cindy M. Goral, Kenneth E. Torrance, Donald P...
) or to simulate different portions of the electromagnetic spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
for the purpose of scientific work. The images simulated are not necessarily more realistic appearing; however, when compared to a real image pixel for pixel, the result is often much closer.
Spectral rendering can also simulate light sources and objects more effectively, as the light's emission spectrum
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....
can be used to release photons at a particular wavelength in proportion to the spectrum. Objects' spectral reflectance curves can similarly be used to reflect certain portions of the spectrum more accurately.
As an example, certain properties of tomatoes make them appear differently under sunlight than under fluorescent light. Using the blackbody radiation equations to simulate sunlight or the emission spectrum of a fluorescent bulb in combination with the tomato's spectral reflectance curve, more accurate images of each scenario can be produced.