Most performant way to graph thousands of data points with WPF?
I have written a chart that displays financial data. Performance was good while I was drawing less than 10.000 points displayed as a connected line using PathGeometry together with PathFigure and LineSegments. But now I need to display up to 100.000 points at the same time (without scrolling) and it's already very slow with 50.000 points. I was thinking of StreamGeometry, but I am not sure since it's basically the same as a PathGeometry stroring the information as byte stream. Does any one have an idea to make this much more performant or maybe someone has even done something similar already?
EDIT: These data points do not change once drawn so if there is potential optimizing it, please let me know (line segments are frozen right now).
EDIT: I tried StreamGeometry. Creating the graphic took even longer for some reason, but this is not the issue. Drawing on the chart after drawing all the points is still as slow as the previous method. I think it's just too many data points for WPF to deal with.
EDIT: I've experimented a bit and I noticed that performance improved a bit by converting the coordinates which were previously in double to int to prevent WPF anti-aliasing sub-pixel lines.
EDIT: Thanks for all the responses suggesting to reduce the number of line segments. I have reduced them to at most twice the horizontal resolution for stepped lines and at most the horizontal resolution for simple lines and the performance is pretty good now.
Answer
I'd consider downsampling the number of points you are trying to render. You may have 50,000 points of data but you're unlikely to be able to fit them all on the screen; even if you charted every single point in one display you'd need 100,000 pixels of horizontal resolution to draw them all! Even in D3D that's a lot to draw.
Since you are more likely to have something like 2,048 pixels, you may as well reduce the points you are graphing and draw an approximate curve that fits onto the screen and has only a couple thousand verts. If for example the user graphs a time frame including 10000 points, then downsample those 10000 points to 1000 before graphing. There are numerous techniques you could try, from simple averaging to median-neighbor to Gaussian convolution to (my suggestion) bicubic interpolation. Drawing any number of points greater than 1/2 the screen resolution will simply be a waste.
As the user zooms in on a part of a graph, you can resample to get higher resolutions and more accurate curve fitting.