High performance graphics using the WPF Visual layer

Question

I am creating a WPF mapping program which will potentially load and draw hundreds of files to the screen at any one time, and a user may want to zoom and pan this display. Some of these file types may contain thousands of points, which would most likely be connected as some kind of path. Other supported formats will include TIFF files.

Is it better for performance to have a single DrawingVisual to which all data is drawn, or should I be creating a new DrawingVisual for each file loaded?

If anyone can offer any advice on this it would be much appreciated.

Answer 1

You will find lots of related questions on Stack Overflow, however not all of them mention that one of the most high-performance ways to draw large amounts of data to the screen is to use the WriteableBitmap API. I suggest taking a look at the WriteableBitmapEx open source project on codeplex. Disclosure, I have contributed to this once, but it is not my library.

Having experimented with DrawingVisual, StreamGeometry, OnRender, Canvas, all these fall over once you have to draw 1,000+ or more "objects" to the screen. There are techniques that deal with the virtualization of a canvas (there' a million items demo with Virtualized Canvas) but even this is limited to the ~1000 visible at one time before slow down. WriteableBitmap allows you to access a bitmap directly and draw on that (oldskool style) meaning you can draw tens of thousands of objects at speed. You are free to implement your own optimisations (multi-threading, level of detail) but do note you don't get much frills with that API. You literally are doing the work yourself.

There is one caveat though. While WPF uses the CPU for tesselation / GPU for rendering, WriteableBitmap will use CPU for everything. Therefore the fill-rate (number of pixels rendered per frame) becomes the bottleneck depending on your CPU power.

Failing that if you really need high-performance rendering, I'd suggest taking a look at SharpDX (Managed DirectX) and the interop with WPF. This will give you the highest performance as it will directly use the GPU.

Answer 2

Using many small DrawingVisuals with few details rendered per visual gave better performance in my experience compared to less DrawingVisuals with more details rendered per visual. I also found that deleting all of the visuals and rendering new visuals was faster than reusing existing visuals when a redraw was required. Breaking each map into a number of visuals may help performance.

As with anything performance related, conducting timing tests with your own scenarios is the best way to be sure.