Introduction - The importance of accurate material visualization
Ocean™ is a realistic rendering software that, based on 3D and material data, provides predictive renderings of complex materials. Ocean™ can handle a large panel of tabulated material data, either theoretical or measured.
In surface characterization, the Bidirectional Reflectance Distribution Function (BRDF) describes, at one point, how light is diffused or reflected by the surface for each angle and wavelength. As shown in Figure 1, BRDF can be described by different contributions: diffuse, glossy, and specular components. A diffuse surface scatters light in all directions, a glossy surface scatters light in preferred directions, and a perfect specular surface, such as a mirror, reflects incident light in a single outgoing direction.
Real materials usually exhibit BRDFs that combine these three categories. Car paints, for example, have a complex appearance due to the presence of flakes inside those paints. Flakes’ properties will introduce a complex glossy component to the appearance. In order to propose predictive appearance image, laboratory measurements of car paint can be done and implemented into Ocean™ .
Understanding BRDF: Theory and components
Specular vs. Diffuse Reflection: Key differences in material appearance
BRDF measurements are necessary to understand how materials interact with light. Specular reflection produces sharp, mirror-like reflections, while diffuse reflection scatters light widely, creating a softer appearance. Glossy reflections fall between these extremes, providing directional but not perfectly sharp reflections. Most materials have a blend of these properties. This is why understanding them is fundamental for achieving accurate digital representations.
BRDF vs. BSDF: Differences and applications
- BRDF (Bidirectional Reflectance Distribution Function): Describes how light is reflected at an opaque surface depending on the incoming and outgoing angles.
- BSDF (Bidirectional Scattering Distribution Function): Expands BRDF by considering both reflection and transmission properties, making it suitable for transparent and translucent materials.
Ocean™ incorporates BRDF and BSDF data to provide highly accurate material visualization. This capability is essential for industries where precise appearance prediction is a requirement to avoid costly physical prototyping and ensure product consistency.
BRDF measurements and implementation in Ocean™
Sample descriptions
In this example, a green car paint sample is studied. A photograph of the sample is presented in Figure 2, under artificial (a) and natural (b) lighting. The sample has a uniform light green color with visible fine flakes and a clear varnish.

Figure 2 - a) Sample photography with artificial light

Figure 2 - b) Sample photography with natural light
BRDF measurements
BRDF measurements are often made using a gonio-spectrophotometer. A spectrophotometer allows for the measurement of the reflection properties of a material as a function of wavelength at different angles. The term “gonio”, from the ancient Greek “gonia” meaning “angle”, indicated that this measurement can be done for different angles, allowing the measurement of the different BRDF components. As shown in Figure 3, the sample is exposed to light from a given direction, and the reflection properties of the surface are measured at several outgoing angles. The two zenithal angles (θin and θout) are varied to capture the full reflection profile.

Figure 3 - Gonio spectrophotometer measurements principle.
An example of measurements, made on the green car paint with a commercial gonio-spectrophotometer is shown in the animation in figure 4. The measurement of the reflection (r [∅]) is shown for each wavelength (see the colorbar), as a function of , for each . The diffuse part of the BRDF is clearly visible and already shows that the sample is green (green is the most reflected color, with the largest r). The data reveal the material’s green appearance, with a prominent diffuse component and a glossy reflection approximately 20° wide.
Due to limitations in gonio-spectrophotometer measurements, the specular contribution is determined with a spectrophotometer that includes an integrating sphere. Flake properties are measured separately with a specialized device.


Figure 4 - BRDF measurements. The right plot is part of the animation on the left side and allow for the description of the measurement.
Integrating BRDF data into Ocean™
Ocean™ is able to directly read and import BRDF data via the BSDF converter toolbox, shown in figure 5. The BSDF (Bidirectional Scattering Distribution Function) extends BRDF by including both reflection and transmission properties. This toolbox allows for splitting the BSDF into diffuse, glossy and specular components, using advanced algorithms. The angular specular/glossy and glossy/diffuse angular limits may be adjusted, highlighted by the green square in figure 5.
When this option is used, the created BSDF is of Additive BSDF type, shown in figure 6, with child BSDFs corresponding to each component (i.e. specular, glossy and diffuse). The specular component was measured using the integrating sphere measurement, while the flake property measurements can be added as a contribution to the glossy component of the BRDF. The “sparkly” BRDF includes the sparkle properties, while the goniophotometer measurements are stored in the Rusinkiewicz tables (used for the glossy and diffuse components).

Figure 5 - Screen capture of the BSDF Converter tool in OceanTM. The green square highlights the option that allows to split the imported BRDF. The red square highlights the parameters that defined the sampling resolution of the imported BRDF.

Figure 6 - Screen capture of the Additive BRDF created by the BSDF converter tools.
The “H Steps / D steps” parameters seen in figure 5 (red square) define the sampling resolution of the imported BSDF, as described in the Rusinkiewicz coordinates system[2]. Choosing an appropriate sampling resolution during import is crucial. As illustrated in Figure 7, oversampling (too small H and D steps) can result in unphysical black lines, while undersampling (too large H and D steps) can produce blurs. Proper sampling ensures accurate digital representations.
The upper part of figure 7 shows the BRDF measurement made with the gonio-spectrophotometer in the Rusinkiewicz coordinates system[2]. The color bar indicated the intensity of the measured reflection.

Figure 7 - Simulation of the car paint as a function of the sampling resolution chosen when importing the BRDF
Simulation results and validation
Results of the simulation are presented in Figures 8 and 9. An in-situ simulation of the material is proposed and shown figure 9. The light green color and sparkles are visibles, in particular in the right image (figure 8) where a zoom of the sample is provided. The light green color and sparkle size closely match the real sample. A quantitative study demonstrated strong agreement between the simulation and the physical sample.

Figure 8 - Left: Simulation result using the green car paint. Right : Zoom allowing to see the small sparkles.

Figure 9 - In situ simulation made using the measured car paint
Conclusion - Achieving accurate digital material simulation
This article explored the study of car paint, which exhibits complex light reflectance behaviors described by BRDF. Measurements, including those using a gonio-spectrophotometer, were implemented into our predictive rendering software, demonstrating a high level of agreement in image quality and color accuracy between real samples and rendered images. Ocean™ is a reliable tool for generating accurate material simulations for industrial materials where faithful appearance is required.
Q&A
What is the difference between specular and diffuse reflection?
Specular reflection reflects light in a single direction (like a mirror), while diffuse reflection scatters it broadly in all directions, creating a softer appearance. Most real-world materials exhibit a combination of both types. Their accurate simulation therefore requires powerful rendering software such as Ocean™, capable of taking into account the detailed optical properties of materials.
Why is BRDF important in material rendering?
The Bidirectional Reflectance Distribution Function (BRDF) describes how light interacts with a material’s surface at different angles, enabling accurate digital representations for visualization and product development. Complex materials such as car paints, glass, and coatings with challenging effects are difficult to render with accuracy without taking into account their BRDF.
How does Ocean™ software simulate complex material effects?
Ocean™ integrates BRDF data, including specular, diffuse, and glossy components, to simulate sparkles, translucency, and color shifts. Combined with powerful path tracing, global illumination technology and advanced computational capacities, it ensures the rendering of physically-true material visualizations.
What are the benefits of using BRDF for prototyping?
BRDF-based digital prototyping allows for:
- Reduced reliance on physical prototypes.
- More accurate color and texture predictions.
- Accelerated decision-making by providing realistic digital representations.
- Minimized costs and material waste.
What tools are used for BRDF measurement?
Common tools include gonio-spectrophotometers and integrating spheres, which capture reflection properties at various angles and wavelengths for precise material characterization.
Can Ocean™ handle materials with color-shifting coatings?
Yes, Ocean™ can simulate color-shifting coatings and other complex material behaviors under real lighting conditions.
How can BRDF data improve the accuracy of virtual product designs?
By integrating precise BRDF data into rendering software like Ocean™, designers and engineers can better predict how materials will appear in real-world lighting conditions, ensuring consistency between digital prototypes and final products.
How can Ocean™ help reduce the time spent on physical prototypes?
Ocean™ provides predictive rendering capabilities that allow stakeholders to visualize and adjust material properties digitally, reducing the number of physical prototypes needed and speeding up the product development cycle.
Looking for a reliable tool that accurately predicts material appearance?
Read about our services & solutions or contact us to learn how Ocean™ can help you reduce prototype costs and speed up decision-making.
Responses