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- Rida T. Farouki, John K. Johnstone
- Computer Aided Geometric Design
- 1994

- Ching-Kuang Shene, John K. Johnstone
- ACM Trans. Graph.
- 1994

In general, two quadric surface intersect in a space quartic curve. However, the intersection frequently degenerates to a collection of plane curves. Degenerate cases are frequent in geometric/solid modeling because degeneracies are often required by design. Their detection is important because degenerate intersections can be computed more easily and allow… (More)

- Joon-Kyung Seong, Gershon Elber, John K. Johnstone, Myung-Soo Kim
- Computing
- 2004

We present an algorithm for computing the convex hull of freeform rational surfaces. The convex hull problem is reformulated as one of finding the zero-sets of polynomial equations; using these zero-sets we characterize developable surface patches and planar patches that belong to the boundary of the convex hull.

- LIN YANG, JOHN K. JOHNSTONE, +5 authors Lin Yang
- 2011

- Rida T. Farouki, John K. Johnstone
- IMA Conference on the Mathematics of Surfaces
- 1992

- John Johnstone, Massimo Fazio, +7 authors Christopher A Girkin
- Investigative ophthalmology & visual science
- 2014

PURPOSE
This study explores variation in the axial location of Bruch's membrane opening (BMO) to determine if this reference plane varies with age and race.
METHODS
There were 168 spectral-domain optical coherence tomography (SDOCT) optic nerve head volumes that were obtained from healthy subjects and manually delineated within 24 axial slices to develop… (More)

- John K. Johnstone
- Computer Aided Geometric Design
- 1993

- John K. Johnstone, Ching-Kuang Shene
- Computers & Graphics
- 1992

- John K. Johnstone, Kenneth R. Sloan
- IEEE Visualization
- 1995

We present a method for constructing tensor product Bezier surfaces from contour (cross-section) data. Minimal area triangulations are used to guide the surface construction , and the final surface reflects the optimality of the triangulation. The resulting surface differs from the initial triangulation in two important ways: it is smooth (as opposed to the… (More)

- Ching-Kuang Shene, John K. Johnstone
- Symposium on Solid Modeling and Applications
- 1991

In general, two quadric surfaces intersect in a space quartic curve. However, the intersection curve frequently degenerates to a collection of plane curves. These degenerate cases introduce problems into the general intersection algorithms and are difficult to implement in a reliable way. In this paper, we investigate this problem for natural quadrics.… (More)