OCEAN and Gonio-apparent coating

OCEAN and Gonio-apparent coating

Coating with changing color through different observation angles, called Gonio-apparent coating, are seeing growing demand on many markets: car paint, steel paint, cosmetic, … Ocean software can easily simulate this type of materials by using measured Bidirectional Reflectance Distribution Function (BRDF).

 

Here we present the results of a study on steel paint samples. First, we measured the BRDF with a Gonio-spectrophotometer . Reflection coefficients are measured for more than thirty wavelengths of the visible light spectrum and for more than five thousand pair of incident and reflected angles. This calibrated data is imported directly into Ocean for complete realistic rendering.

 

To assess rendering accuracy, we use comparisons with photos, taken at several angles of the sample in a dedicated light box. This light box is an important part of the quality process, allowing for a highly controlled light environment in the scene and for 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 also been measured. Standard color checker is used to normalize white balance and colors of renders and photos. No other post-processing and no image processing editor have been used on any of the resulting images.

 

Illustration 1: Comparison between photos (top) and renders (bottom). 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 are the photos and bottom are the renders. The color variation through different angles is easily observable and the color matching accurate.

 

Ocean is perfectly adapted to simulate and predict this type of Gonio-apparent coating.