Ellipse EvoluteHere we see a collection of lines that are normal to an ellipse. The points were nearby normals intersect are the centers of the circles of curvature for the ellipse. These centers lie along the focal curve, or evolute for the curve. In the case of an ellipse, the evolute is an astroid, which we can see in the image as a light caustic in the form of a glowing, four-pointed "star". This image is from Beyond the Third Dimension, and is closely related to Ellipse Spotlights and Sandpile Chalice. The normals to an ellipse were a central theme within the video Fronts and Centers. |
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