Parabolic Sphere Tracing of Signed Distance Fields for Old Glass Modelling and Rendering.

Area of Science:

• Computer Graphics
• Material Science
• Architectural History

Background:

• Artisanal glass production creates unique visual characteristics due to surface and volume irregularities.
• Historical glass, particularly in medieval to 18th-century architecture, exhibits variations like bubbles and refractive index changes.
• Accurate digital representation of these historical glass objects is challenging.

Purpose of the Study:

• To develop a unified framework for modeling and rendering irregular and heterogeneous glass objects.
• To accurately simulate the visual appearance of historical glass, focusing on stained glass.
• To enable the creation of complex 3D models of historical glass artifacts.

Main Methods:

• Utilizing signed distance functions and analytic solutions for ray tracing within tetrahedral volume elements.
• Applying Fermat's principle and seismic ray theory to develop an unbiased estimator for transmitted lighting.
• Employing texture coordinates to map complex glass panel sections onto mesh faces for detailed rendering.

Main Results:

• A method to account for diverse glass irregularities (bubbles, surface variations, refractive index changes) in a unified framework.
• Demonstration of an unbiased estimator for transmitted lighting through complex glass panels.
• Successful modeling and rendering of 3D objects composed of colored glass facets, such as stained glass windows.

Conclusions:

• The proposed method effectively models and renders historical glass, capturing its unique visual properties.
• This approach provides a robust tool for digital reconstruction and analysis of historical architectural glass.
• The technique facilitates the creation of realistic digital assets for applications in historical preservation and virtual environments.