Draw Custom OHLC Plots using OnRender

[Guest]

Hello,
I am trying to draw Custom OHLC Plots using OnRender:
https://gist.github.com/Zz9uk3/4c3f6...7a3ba0a178e395

For some unknown reason the low and the high point are a bit off from the default drawn OHLC plots by the configured data series. Moreover the left and right tick of open and close are sometimes to small:

https://i.imgur.com/kFgG7Hp.jpg

Does anyone know what I am doing wrong here or how I can account for the difference between the default OHLC plots and my plots?

[Guest]

Here is a video of the default plot getting bigger as soon as I stretch the horizontal axis:

https://i.imgur.com/wmH6aZB.gifv

[NinjaTrader_JoshG]

Hello mrzz93,
Thanks for your post.

I do not see anything right off the bat, and I am unable to test the GitHub snippet.

Can you add some prints and see what values are getting passed in versus what is appearing on the chart?

[Guest]

Hey Josh! Thanks for your reply
The solution was to first of all acknowledge that if the width is under 1 OnRender wont draw line. So I came up with the following to always keep my plots visible:

float barPixelWidth = (float)chartControl.BarWidth;
if (barPixelWidth < 1) barPixelWidth = 1;

Lates on I added the barPixelWidth to the top and low of the points I choose for my lines:

var yHigh = chartScale.GetYByValue(high) - barPixelWidth / 2;
var yLow = chartScale.GetYByValue(low) + barPixelWidth / 2;

Now the low and top end of my OHLC candle always aligns perfectly.

I also monitored the values closely and they were always equal which makes me believe NT also adds a few numbers to the top and bottom of the OHLC bar drawn for the DataSeries.

[NinjaTrader_JoshG]

mrzz93,

Happy to help. Thanks for sharing!

[stupiddove]

var yHigh = chartScale.GetYByValue(high) - barPixelWidth / 2;
var yLow = chartScale.GetYByValue(low) + barPixelWidth / 2;

Thank you for sharing.

JoshG, I don't understand. Why do we have to add/subtract "barPixelWidth / 2" for the correct alignment? Doesn't chartScale.GetYByValue(high) give the exact y position of high?

[NinjaTrader_ChrisL]

Hi, thanks for posting.

barPixelWidth / 2 places the point in the center of the bar no matter what the width setting for the bar is.

Best regards,
-ChrisL

[stupiddove]

ChrisL, thank you for your reply.

I don't quite understand. The function "chartScale.GetYByValue()" returns the chart's y-pixel coordinate of the price value. If I input the close px, I will get the y-pixel coordinate of that close px, I override onRender() that a white line is placed on each primary price bar.

private void CreatePlot(ChartControl chartControl, ChartScale chartScale, int barIndex)
{
    // get x-coordinate
    int x = chartControl.GetXByBarIndex(ChartBars, barIndex);

   float barPixelWidth = (float)chartControl.BarWidth;

   double high_px = High.GetValueAt(barIndex);
   double low_px = Low.GetValueAt(barIndex);

   float y_high = chartScale.GetYByValue(high_px);
   float y_low = chartScale.GetYByValue(low_px);

   SharpDX.Direct2D1.SolidColorBrush barBrushDx = new SharpDX.Direct2D1.SolidColorBrush(RenderTarget, SharpDX.Color.White);
   barBrushDx.Opacity = 0.8f;

   SharpDX.Vector2 v_high = new SharpDX.Vector2(x, y_high);
   SharpDX.Vector2 v_low = new SharpDX.Vector2(x, y_low);

   RenderTarget.DrawLine(v_low, v_high, barBrushDx, (float)ChartControl.BarWidth);

   barBrushDx.Dispose();

}

The result is:




Why are the white bars not covering the price bar from high to low?

[NinjaTrader_ChrisL]

Hi, thanks for your reply.

The OHLC chart style is available to study through NinjaScript Editor>ChartStyles>OhlcStyle.cs file. In the OnRender method for this chart style there is some slight modifications to the high/low values, if you mimic the renering techniques used here it should match up e.g.:
point0.X = point1.X = x;
point0.Y = high - lineWidth * 0.5f;
point1.Y = low + lineWidth * 0.5f;

Best regards,
-ChrisL

[stupiddove]

I see, thank you for your help.