The above image is from an application that uses Hermite splines to model a string with finite elements. Absolute constraints are used to pin the endpoint and tangent of each finite element to the next, and to pin elements to collision points with pegs. Desired constraints are used to indicate that the string should fall at a certain rate and that it should maintain a certain relative bendiness and stretchiness. A linear solver written by Cindy Grimm is used to solve for both sets of constraints simultaneously. In the image below, the point and tangent controls for the Hermite curves that compose the finite elements are visible. In the application, the nodes, tangents, and pegs can be manipulated interactively while the application simulates the dropping of the string. Cyan pegs are those with which the string has collided. This application runs in real time on a Sun Ultra.
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