OCEAN and Gonio-apparent coating

OCEAN and Gonio-apparent coating

Coating with changing colour through different observation angles, called gonio-apparent coating, are growing-up on many markets, car paint, steel paint, cosmetic, … Ocean software is able to simulate such kind of material by using measured Bidirectional Reflectance Distribution Function (BRDF).

 

Here we present the results of a study on steel paint sample. First, we measure the BRDF with the gonio-spectrophotometer . Reflection coefficients are measured for more than thirty wavelength of the visible light spectrum and for more than five thousand pair of incident and reflected angles. Such data are imported into Ocean to make realistic rendering.

 

To assess the render, we make comparisons with photo, taken at several angle, of the sample in a dedicated light box. Light box is an important point to highly control the light environment in the scene and allow an accurate comparison between renders and photos. Light sources are five halogen bulb emitters placed back to a plastic scattering plate. Walls and floor are grey Lambertian surfaces. Reflection spectrum on the walls and floor of the light box have been measured. Standard colour checker have been used to normalized white balance and colours of renders and photos. No other post-processing and no image processing editor have been applied on both, renders and photos.

 

Illustration 1: Comparison of renders and photos. Top are the photos and bottom are the renders. Left to Right shows different observation angles.

 

Illustration 1, present the result of this study. Each column show a different observation angle and rows are related to  the comparison. Top row are the photos and bottom row are the renders. The variation of the colour through the different angle is well observed and the matching of the colour is pretty nice.

 

Ocean is perfectly adapted to simulate and predict such kind of gonio-apparent coating.