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Ellipse Marker not drawing correctly


I try using the EllipsePointMarker with the following code

new EllipsePointMarker
   Width = 4,
   Height = 4,
   StrokeThickness = 2

the markers usually draw looking like a plus sign or a diamond.

It only looks like a circle if I use a Width and Height of 8.

See attached.

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Best Answer

Hello Mike,

To answer your question, it appears the StrokeThickness is the problem. The method to draw lines > 1 thickness in ‘High Speed’ mode uses a bresenham algorithm, which can’t be antialiased, so when you have a small ellipse, 4px, with a 2px stroke, you end up with a little plus-shaped marker instead. Removing or reducing the stroke-thickness will greatly help in this instance. So I would try stroke thickness = 1 or even 0 with such small markers when using the High Speed rasterizer.

Olya is right about High Quality mode – this has sub pixel (floating point) rendering algorithms and is much better looking, but will have a performance impact. After much research and development, we have built (and is almost ready to ship) a Direct3D10 Renderer which is as fast as (or faster in some cases) than the High Speed rasterizer but has the quality of High Quality. It will only support DX10 and above on Windows Vista and above. If that’s of interest to you, get in touch, I can arrange a pre-release to do some testing.

Kind regards,

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Hello there,

Thanks for contacting, we’ll try to be a help.

First of all, if you want your series & PointMarkers to be crisp and (round in your case) we could suggest switching Rasterizer to High Quality mode. We tried
Width = 4,
Height = 4,
in High Quality and it looks much better, and it is round.

Let us know if this helps to get what you expected,
if it’s not – don’t hesitate to ask for further assistance.

Best regards,
– Olya

  • Mike Melancon
    Can you tell me how to change the rasterizer?
  • Mike Melancon
    Also, how slow is this going to make the chart? Is it really impossible to draw a circle using the high speed rasterizer? The chart is already too slow for us in it's current state. Making it slower is not an option.
  • Olya
    Hi Mike, Getting back to your enquiry, well, you could see how High Quality rasterizer can be used in our Use High Quality Rendering example. However, High Quality mode really makes the chart slower, so probably it wouldn’t go in your case. What we can suggest using here is the custom PointMarker. We’ve got a ‘SpritePointMarker’ which you can see in Using PointMarkers example, so the option is to modify it into a simple circle. This way you’ll get a circle and will preserve the speed. Let us know whether it can be a solution, or if we can be of any further help. All the best, - Olya
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