"Generating Surface Crack Patterns"

We present 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 a comparison with photographs of real-world examples. Using a physically based approach also enables us to generate animations similar to time-lapse photography.

Iben, H. N. and O'Brien, J. F., "Generating Surface Crack Patterns." In The Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation, pages 177-185, Vienna, Austria, September 2-4, 2006.

This paper received an Honorable Mention in the Best Paper Award at SCA 2006.

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Examples

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A "crackle glass" dragon, generated by uniform shrinkage of the surface.	Example of a "crackle glaze" teapot, generated by initializing the stress field to uniform shrinkage and evolving it by adding uniform tension.


Cracks generated from initializing the stress field with a pattern modeling impacts in flat glass. The field is evolved by the relaxation process, causing the cracks to propagate.	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.


Curvature can be used to control crack formation, as demonstrated here. Notice the high concentration of cracks around areas of high curvature, such as the ears, neck and leg.	This image was generated using only uniform shrinkage of the surface, resulting in more evenly spaced cracks than the image on the left.


Another example demonstrating an artistic effect achieved by using curvature to bias the concentration of cracks.	Example of adding a curling effect to the cracked mud below (bottom row).

Comparisons with photographs:

A rendered example of a "crackle glaze" cup (left) compared to a photograph (right). Our algorithm generates this effect by initializing the stress field to uniform shrinkage over the surface and evolving it with uniform tension.


A rendered example of dried mud (left) compared to a photograph (right). We used uniform shrinkage of surface and set alpha = 0.85 to propagate the cracks further.	Photograph copyright Mayang Adnin


As in the example above, we used uniform shrinkage of the surface, but changed the parameter alpha = 0.5 to demonstrate controlling the crack propagation.	Photograph copyright Mayang Adnin