Introduction
Identifying, quantifying, and tackling such parasitic reflection effects appears as a must have while developing the car. However, it requires to have access to the full vehicle with interior materials integrated. This requirement is not always easy to access as there are only a limited amount of vehicles built during the carline development phases. Consequently, undesired parasitic effects would be observed often too late, without the possibility of turning back.
Alternatively, based on the 3D data of the car and respective materials optical characteristics, virtual prototyping can faithfully render such situations in different lighting conditions, environment, and point of view. It will help the user saving time, budget and tackling this issue in early development phases.
Designing modern automotive interiors requires more than aesthetics—it demands precise control of glare and parasitic reflections to ensure driver comfort and safety, which can now be achieved early using real-xworld data of car interior materials and environment with spectral and texture-based simulation.
In the following blog article, we considered two case studies aiming at illustrating how Ocean™, optical simulation software can support automotive OEM and Tier 1 in pointing out parasitic reflection issues and identifying associated counter measures.
Case 1 - Reducing glass roof reflections with Low-E coating simulation in Virtual Prototyping
To reduce parasitic reflections on glass surfaces in car cabins, we evaluated different low-e coatings using virtual prototyping with spectral optical data, helping automotive teams simulate reflective surfaces and make informed material choices early in the design phase.
Figure 1 – (a) Laminated privacy glass (RL 7%). (b) CVD coated laminated privacy glass (RL 4%). (c) PVD coated laminated privacy glass (RL 2%).
- Privacy roof without any coating – RL 7% (a)
- Privacy roof with low-e CVD (Chemical Vapor Deposition) coating – RL 4% (b)
- Privacy roof with low-e PVD (Physical Vapor Deposition) coating – RL 2% (c)
In order to assess the visual impact of the choice of CVD coated glass vs PVD coated glass on parasitic reflection, predictive appearance study using Ocean™ got launched. Results are displayed on Fig 2. and Fig. 3. The point of view was set in order to have a direct view on the reflected element of the front cluster on the glass roof. Each coating data was introduced based on their transmittance and reflectance spectra at different incidence angle (0-90°). Simulations was performed considering both day and night lighting conditions and with uncoated laminated glass, 7% reflection, as a reference. In addition, in order to extract quantitative data, the irradiance received by the simulation sensor, i.e. amount of light received by the sensor, was calculated for each case.
Based on the aesthetics renders (Fig. 2-3 a,b,c), the PVD 2% coated glass roof slightly exhibits the less parasitic reflections for both day and night conditions. From a quantitative perspective (Fig 2-3 d), based on irradiance map, a 5% decrease in terms of reflected elements on the glass roof is observed while dealing with PVD coating. Therefore, it can be concluded that PVD coated glass roof should minimize the risk of disturbance for the driver.
While this output could have been coined as PVD coating exhibits the lower RL (2% for PVD against 4% for CVD), the appearance evaluation remains necessary. Indeed, PVD coating is expected to be more expensive than CVD coating and therefore trustable aesthetics simulation of the roof allows to fully justify the additional price.
Figure 2 – Parasitic reflection assessment in daylight conditions for (a) uncoated laminated privacy glass, (b) CVD coated laminated privacy glass, (c) PVD coated laminated privacy glass. In addition, irradiance map (d) is calculated for each case.
Figure 3 – Parasitic reflection assessment in night conditions for (a) uncoated laminated privacy glass, (b) CVD coated laminated privacy glass, (c) PVD coated laminated privacy glass. In addition, sensor irradiance map (d) is calculated for each case.
Case 2 - Dashboard glare analysis: Simulating textured materials for improved driver visibility
This second case study aims at understanding the impact of different dashboard textured materials in terms of light reflection on the car windshield and over the car cabin. For this purpose, three configurations got considered for which only the surface textures were varied (Fig. 4) while the material remains the same, diffusive black plastic. Each texture was characterized using XRITE TAC 7 technology in view of the integration into Ocean™. The diffusive black plastic was assimilated to a black Lambertian material.
Figure 4 – The three different plastic textures considered in the present case study.
The dashboard material item got created into Ocean™ and integrated on a Renault Megane 3D geometry which was bought on the internet. Daylight conditions only were considered using a HDRI environment map. The results are displayed on Fig. 5.
From Fig. 5, it can be seen that depending on the material texture, the light interaction will be different. Indeed, it can be observed that the specular and diffuse reflection will be impacted by the surface topography. As a result, different light spreading will occur over the car, on the windshield and will impact differently the driver attention. In addition, it should be pointed out that it the choice of the texture will affect the final appearance of the dashboard. Therefore, a compromise should be established between disturbance risk and aesthetics.
A glare impact assessment could be easily run using Ocean™ in order to better precise the risk for the driver. In addition, it is noteworthy that other features would be expected to impact the final result : environment conditions, reflection by other materials inside the case, driver size, etc. These additional cited elements can be easily integrated into the Ocean™ model.
Figure 5 – Appearance renders of the front cluster of the Renault Megane considering the three different textured materials
This case highlights how dashboard glare analysis can be performed by combining surface texture measurements and spectral data to simulate interior lighting and reflections, allowing designers to predict glare from textured materials and improve both appearance and driver visibility.
Identifying and reducing glare inside car interiors
While minimizing parasitic reflections is a key driver of visual comfort, addressing glare—the excessive brightness or contrast that disrupts visibility—is just as critical. Glare risks often stem from complex interactions between surface texture, material composition, and environmental lighting.
Ocean™ enables designers and engineers to go beyond purely visual evaluations by combining spectral measurements with surface texture capture, ensuring predictive results that reflect real-world behavior. This approach is especially valuable in the context of windshield reflections and dashboard materials, where both micro-texture and spectral reflectance impact driver comfort.
Learn more about our glare simulation capabilities and how Ocean™ combines texture and spectral data for accurate materials simulation.
Conclusion
This blog article highlighted the benefits of using virtual prototyping for assessing parasitic reflection inside car cabin in early carline development phases. Considering proper materials data and a given 3D geometry, Ocean™ offers the possibility to precisely render the interior of the car and identifying from both a qualitative and a quantitative perspective, the risk of parasitic reflections.
Such approach is of particular interest while selecting interior car materials. Each suspicious material, from a reflection point of view, can be easily evaluated provided the virtual prototyping model is created. In case of a glare risk and disturbing behavior identified, Ocean™ allows to probe quickly alternatives and to take efficient counter measures without the needs of building any physical part.
Finally, it is noteworthy to stress that such a virtual prototyping approach allows to drastically diminish the amount of physical prototype and does not require to have access to physical car. This enables saving time and money over a complete project. On the top of this, the as-created virtual prototype facilitate discussion between different development departments.
By using Ocean™ to simulate parasitic reflections and glare in automotive interiors, design and engineering teams can make informed decisions early in development, improving visibility and reducing costly physical prototypes through a reliable optical simulation workflow.
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