Accurate physics-based digital reproduction of effect coatings

Area of Science:

• Materials Science
• Computer Graphics
• Color Science

Background:

• Accurate digital visualization of effect coatings is challenging due to complex optical phenomena like metallic effects, sparkle, and iridescence.
• Existing rendering methods often struggle to capture the full visual appearance, particularly the angular dependence of color (color flop) and texture.

Purpose of the Study:

• To develop and validate an improved 3D rendering framework for accurate visualization of effect coatings.
• To assess the framework's ability to reproduce key visual attributes: color, color flop, and texture (sparkle, graininess).
• To compare the rendering accuracy for flat versus curved samples.

Main Methods:

• Utilized spectral reflectance measurements and sparkle indexes from a multi-angle spectrophotometer (BYKmac-i).
• Employed physics-based flake reflectance models and a sparkle model within the rendering framework.
• Validated rendering fidelity through psychophysical methods, comparing digital renderings with real samples under controlled lighting (Byko-spectra effect light booth).

Main Results:

• Rendering accuracy for color flop was higher with curved samples (93% acceptability) compared to flat samples (80% acceptability).
• Visual tests on 30 metallic samples demonstrated high overall visual acceptability (90%) for the digital reproduction of color and texture.
• Optimized sparkle model parameters using measurement data and a matrix-adjustment model.

Conclusions:

• The developed 3D rendering framework significantly improves the accurate visualization of effect coatings, including complex visual attributes.
• The use of curved samples enhances the accuracy of rendering color flop.
• The framework provides a reliable method for digital reproduction of effect coating appearance, achieving high observer acceptability.