Generating Surface Cracks
Hayley Nicole Iben and James O'Brien
Apple Computer, Intel, Sony, UC MICRO, GAANN Fellowship, National Science Foundation, Pixar Animation Studios, Autodesk and Alfred P. Sloan Foundation
This project presents a method for generating surface crack patterns that appear in materials such as mud, ceramic glaze, and glass. To model these phenomena, we build upon existing physically-based methods. Our algorithm generates cracks from a stress field defined heuristically over a triangle discretization of the surface. The simulation produces cracks by evolving this field over time. The user can control the characteristics and appearance of the cracks using a set of simple parameters. By changing these parameters, we have generated examples similar to a variety of crack patterns found in the real world. We assess the realism of our results by comparison with photographs of real-world examples. Using a physically-based approach also enables us to generate animations similar to time-lapse photography. We present the details of our algorithm in .
Figure 1: Left: a "crackle glass" dragon modeled by initializing the stress field to uniform shrinking of the surface; Right: cracks generated from initializing the stress field with a pattern modeling impacts in flat glass. The stress field is evolved by the relaxation process, causing the cracks to propagate.
Figure 2: Left: example of a "crackle glaze" teapot, generated by initializing the stress field to uniform shrinkage and evolving it by adding uniform tension; Right: a rendered example of dried mud, generated by uniformly shrinking the surface
Figure 3: Left: As an artistic effect, we initialized the stress field to uniform tension with some bias to crack in the principle curvature directions. The result of using this heuristic is demonstrated by the vertical cracks of the angel's arm and the cracks following the folds of fabric. Right: Another example demonstrating an artistic effect achieved by using curvature to bias the concentration of cracks
- H. N. Iben and J. F. O'Brien, "Generating Surface Crack Patterns," Proc. ACM SIGGRAPH/Eurographics Symp. Computer Animation, Vienna, Austria, September 2-4, 2006, pp. 177-185.