<p>Iridesence can be seen in several variations: diffraction as seen in CDs and DVDs (see Stam's SIGGRAPH 1999 paper on this), phase shifting and modulation in multi-layered surfaces as you see in oilspills on water, or structural coloration as you see in butterfly wings. (Also there is the related pearlescence). However, it's not trivial in any way, probably worth a paper or two.</p>

CC BY-SA 4.0
2018-08-20T06:43:40.957Z
2018-08-20T06:43:40.957Z
beyond
<p>I have little knowledge of this topic but from what I gather in a Ray Tracer each ray is given its own wavelength as opposed to an RGB value. This automatically simulates Dispersion and Fluorescence. Is this called Spectral Rendering?</p>

<p>What are the approaches usually taken to render Iridescence? Could someone give a brief overview of the method and a reference to a resource I can use to learn more in-depth knowledge I can use for implementation? </p>

CC BY-SA 3.0
2017-06-26T13:18:26.693Z
Correct. This is called spectral rendering. The easiest implementation is to assign a wavelength to each starting ray and then reflect, refract, etc. as per normal. The BRDF / fresnel would then take the wavelength as an additional parameter. This would automatically handle Iridescence.
RichieSams
<pathtracing><physically-based><spectral>
How is Iridescence handled in a Path Tracer?
Arjan Singh
# How is Iridescence handled in a Path Tracer?

(Asked by: username_0 on 2017-06-24)

I have little knowledge of this topic but from what I gather in a Ray Tracer each ray is given its own wavelength as opposed to an RGB value. This automatically simulates Dispersion and Fluorescence. Is this called Spectral Rendering?

What are the approaches usually taken to render Iridescence? Could someone give a brief overview of the method and a reference to a resource I can use to learn more in-depth knowledge I can use for implementation?

**Tags:** pathtracing, physically-based, spectral

> **Comments:**
> **username_1**: Correct. This is called spectral rendering. The easiest implementation is to assign a wavelength to each starting ray and then reflect, refract, etc. as per normal. The BRDF / fresnel would then take the wavelength as an additional parameter. This would automatically handle Iridescence.  

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## 1 answers

### Answer by username_2 on 2018-08-20. Score: 1

Iridesence can be seen in several variations: diffraction as seen in CDs and DVDs (see Stam's SIGGRAPH 1999 paper on this), phase shifting and modulation in multi-layered surfaces as you see in oilspills on water, or structural coloration as you see in butterfly wings. (Also there is the related pearlescence). However, it's not trivial in any way, probably worth a paper or two.


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