On Wed, 15 Jun 2011, John Peterson wrote:
On Wed, Jun 15, 2011 at 11:58 AM, Roy Stogner <[email protected]> wrote:Here's the problem: how do we get such a test to avoid false negatives on elements with curved (i.e. potentially bulging out of the bounding box) sides? I've got the svn head using a bounding box test only on first-order elements, which should work (first-order hexes can have curved sides, but the curves never extend outside of the bounding box), and that's better than nothing, but I'd like a test (even an alternate less discriminating test) applicable to higher-order geometric elements.If the side bulges out, is a mid-edge or mid-face node on that side not guaranteed to be at the farthest-out point (and thus define the new bounding box)?
Nope. Picture a three noded edge at (0,0), (1,1), and (2,1). ymax for the bounding box is 1; ymax for the edge is at (3/2, 9/8). It seems like there ought to be a safe cheap formula for expanding the bounding box, but it's not going to just be some function of ymin and ymax in the y direction. Imagine if that first point is moved from (0,0) to (1-epsilon,0). --- Roy
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