> Does NSBezierPath do decimation as well as interpolation? I didn't find it in > the Class Reference.
It does whatever it needs to do in order to achieve "great" results, where "great" is in practical terms something like "an order of magnitude finer than pixel resolution". Last I checked, it did not do any filtering - if you feed it a billion points that happen to represent a single line, it will perform as if for a billion points, not two. > In my application, the math generates hundreds of points for accuracy, for > every one that needs to be plotted to make a decent looking plot. Signal > processing theory says that you can't just throw away points, or you can > generate errors. Indeed. The question is how large those errors are compared to the pixel resolution. > For example, I might generate 25,000 points and be happy to look at a 200 > point plot. Throwing 25,000 points at NSBezierPath might swamp it, or at > least run very slowly. NSBezierPath can handle millions of points in certain circumstances. Where by "handle" I mean draw the path in a time on the order of hundreds of milliseconds. That said, if you can pre-filter your path so that you don't provide unnecessary points (considering the output resolution) you might save yourself and your users a lot of waiting. FWIW a trivial "is this point greater than 0.1 pixels away, in Cartesian distance" drop filter has worked well for me in the past, producing results that are essentially visually indistinguishable. It has it's weakness, obviously, but tends to work well on "real world" data (i.e. data that isn't extremely high frequency and amplitude relative to the view size). And when it doesn't work so effectively, users tend to prefer the visual accuracy over performance, since the difference in those cases can be so significant. But your users may vary. FYI if your line width is one pixel or lower NSBezierPath uses a much faster algorithm (as in, several orders of magnitude faster, in some circumstances). So keep that in mind. Also keep in mind that the vast majority of its time, for many-point paths, is spent determining intersections. If you can render your overall path in segments via multiple NSBezierPaths, that'll be much faster. Also, NSBezierPath caches a lot of key info, so hold on to your references if you can reuse them. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
