How does Mie scattering affect material appearance?
Mie scattering is a physical phenomenon that describes how light interacts with particles whose size is comparable to the wavelength of visible light. It plays a role in determining the color, haze, translucency, and brightness of real materials such as coatings, plastics, glass, and biological tissues.
Materials, appearance is not governed only by surface reflection. Volumetric light transport has also an impact on the optical behavior, where light is scattered multiple times by internal particles, pigments, or microstructures before reaching the observer.
Because Mie scattering is strongly wavelength-dependent, it directly influences how different colors propagate through a material. This makes it a key mechanism for understanding effects such as milky appearance, reduced contrast, opacity, or structural coloration.
Accurately predicting these effects demands a physically based, fully spectral optical simulation framework capable of modeling light–matter interactions at the particle level.
This article explains how Mie scattering works, where it appears in engineering applications, and why it is essential for predictive material appearance simulation.
Back to the basics of light
Colors in the visible light spectrum are characterized by different wavelengths ranging from 380 nm (violet/blue) to 780 nm (red color). Such a split can be observed by passing white light (superposition of lights of different wavelengths) through a prism or simply by observing rainbows (Fig. 1). While considering light-matter interactions, all wavelengths might not behave similarly. Depending on the physical/chemical nature of the materials, specific wavelengths can be either transmitted, either absorbed, either reflected. The deflection of the light (refraction) appears to be as well wavelength dependent. These optical effects lead to the understanding of coloration processes as described here below.
Figure 1 : Light dispersion by a prism.
Generally speaking, it is necessary to distinguish between the colors that depend on the chemical nature of an object and those that do not.
The first case considers the selective absorption of light. When striking an object, certain range of wavelengths are absorbed by specific molecules, e.g. pigments or dyes. The origin of the perceived color in this context arises from the collection of the radiation that is not absorbed but instead reflected by the object.
In the second case, independently of the chemical nature, physical phenomena such as refraction, interference and scattering of light are responsible for the observed colors, known as structural coloration. In this specific case, colors are produced when a material is formed of one or more parallel thin layers, or otherwise composed of nano/microstructures on the scale of the color’s wavelength. The latter case is the origin of Mie scattering coloration.
What is Mie scattering?
The coloration produced by Mie scattering arises from the scattering of the light by homogenous sphere sized from few nanometers to hundreds micrometers. The underlying physical process consists in the absorption of light by nano/micro spheres followed by its re-emission in different directions with different intensity. In nature, Mie scattering takes place in the lower 4.5 km of the atmosphere, where there may be many essentially spherical particles present with diameters approximately equal to 1 to 10 µm. For instance, cloud droplets scatter all wavelengths of the visible light creating the white appearance of the cloud.
Depending on the size, density, distribution of the spheres, the incidence angle of the light, the refractive index of the sphere and the distance to the observer, the intensity of the scattered light will be different for each wavelengths. This phenomena is illustrated here below by the render in Fig. 2 with gold/silver nanoparticles of variable size immersed (10nm to 100 nm) in liquid (colloidal solution). Depending on the particle size, it can be seen that the colorimetry will be different from one colloidal solution to another.
Figure 2 : Colloidal silver (left) and (gold) with various particle size (10 to 100nm). The renders are made by OceanTM Mie scattering : rendering examples made by OceanTM
Mie scattering is part of the OceanTM rendering tool box and allows to play on a large set of relevant parameters in the simulation: sphere refractive index, sphere distribution, sphere size, …. In order to illustrate the use of this theory, several examples are presented here below.
1. Mixed fluids
The optically important elements in milk include vitamin B2, fat globules and proteins. The host medium is water in which many different components are dissolved. The component exhibiting the most significant absorption in the visible range is vitamin B2. The optical contribution of each elements is displayed in Fig. 3 through the renders made by OceanTM. The Mie scattering occurs when adding in the composition the protein and the fat globules. It can be seen that the protein are more likely to diffuse blue hue while fat globules diffuse white opaque colors. This is due to the size of the fat globules which are much bigger than the proteins. As the fat globules concentration is much higher than the protein’s one, the milk appears white. Moreover, the greater the concentration of fat globules, the more diffusive is the milk as it can be seen on Fig. 3 while considering skimmed milk, regular milk, and whole milk.
Figure 3: Rendered image made by OceanTM of the components in milk as well as mixed concentrations. From left to right the glasses contain: Water, water and vitamin B2, water and protein, water and fat, skimmed milk, regular milk, and whole milk.
2. Alga and minerals concentration in the sea
The concentration of alga and minerals in the sea is not the same everywhere in the world. As a consequence, the Mie scattering caused by those elements is not the same, causing a difference in the perception of subsea components. As an illustration, submarine view renders from different sea is displayed in Fig. 4. It can be seen that depending on the concentration of alga both the diffusion and the colorimetry of the water is affected. As a result, the water will appears either clear, either troubled with a color either blueish, either greenish.
Figure 4 : Submarine view renders from different sea made by OceanTM.
3. Colored minerals
In order to illustrate the impact of both the refractive index and the size of the particles, renders of metallic sphere with variable size in glass medium were realized (Fig. 5). From left to right : 40 nm silver spheres, high density of 40 nm silver spheres, 60 nm gold sphere, cranberry glass (mixed of molten glass and gold sphere). The caustics , which are the envelope of light rays reflected or refracted by a curved surface or object, can be observed on the render. This latter topic will described in another article. Moreover, bichromic behavior of the minerals can be observed. This feature corresponds to specific optical effects for which the absorbed and scattered light can lead to complementary color. It can be especially observed for the 60nm gold sphere for which transmitted light is mainly blue/green, while the scattered light is primarily red in color.
Figure 5 : Renders of metallic sphere with variable size in glass medium made by OceanTM. From left to right : 40 nm silver spheres, high density of 40 nm silver spheres, 60 nm gold sphere, cranberry glass (mixed of molten glass and gold sphere).
Engineering applications of Mie scattering
Material appearance and coatings
In coatings, plastics, and paints, scattering by pigments or fillers determines key appearance properties:
- opacity and hiding power
- brightness and whiteness
- haze and clarity
- color saturation
Latex paints, for example, rely heavily on particle scattering to control how light diffuses through the coating.
Understanding scattering behavior helps engineers design formulations that achieve the desired optical performance.
Optical characterization and particle measurement
Mie scattering is widely used to measure particle size and concentration.
Instruments such as nephelometers, particle sizers, aerosol analyzers analyze scattered light patterns to determine the characteristics of particles suspended in air or liquids.
These techniques are essential in:
environmental monitoring
industrial process control
pharmaceutical production
Biomedical optics and tissue imaging
Biological tissues contain structures such as cell nuclei, organelles, and membranes whose dimensions are comparable to visible wavelengths.
As a result, tissue appearance and light propagation in biological media are largely governed by Mie scattering.
This phenomenon plays an important role in techniques such as optical coherence tomography, tissue diagnostics, laser-based therapies
Understanding scattering mechanisms helps improve both imaging accuracy and diagnostic capabilities.
Atmospheric and remote sensing
Mie scattering is also fundamental in meteorology and remote sensing.
Cloud droplets, aerosols, and dust particles scatter sunlight in the atmosphere, influencing:
visibility and haze
satellite observations
lidar measurements
Because particle sizes are often comparable to visible wavelengths, Mie scattering dominates in cloudy or aerosol-rich conditions.
Accurate atmospheric modeling therefore requires realistic scattering models.
Conclusion
As we have seen, the diffusion of Mie is a omnipresent mechanism with a strong impact on appearance. In fact, being able to predict the optical properties of such materials is a real technical advantage: Indeed, thin films or solutions based on nanoparticles (ZrO2, TiO2, …) are increasingly used in industry for their innovative optical properties. Whether for aesthetic or technical use. In both cases, the appearance of these films or their interactions with other (composite) materials can be finely predicted.
In addition, these diffusion/absorption mechanisms may also have a role in the environment, as in the example of seawater. But atmospheric conditions such as snow, pollution or fog are just as many cases that fall within the scope of Mie’s theory. In fact, simulating these conditions and phenomena with precision provides a high degree of reliability to the simulations.
Predictive optical simulation therefore requires a fully spectral, physically grounded pipeline that combines:
- volumetric scattering models based on Mie theory
- spectral light transport
- physically accurate material data
- realistic illumination conditions
Only by capturing this complete physical chain can simulations remain valid when materials, lighting, or geometry change.
More about Ocean™'s physically-true framework:
Spectral light transport and geometric optics for physically true simulation
Geometric optics provides the first-order physical description of light transport by modeling light as energy-carrying rays propagating through space and interacting with interfaces and volumes. While geometric optics alone is not sufficient to describe all optical phenomena, it defines the essential structure upon which Ocean™’s spectral radiative transfer, material interaction models, and perception pipelines are built.
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