ProEssentials WPF Delaunay Triangulation — 2D Contour from Scattered Points

A ProEssentials v10 WPF .NET 8 demonstration of Delaunay triangulation contour rendering using PesgoWpf — the ProEssentials scientific graph object for continuous numeric X and Y axes.

➡️ gigasoft.com/examples/147

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What This Demonstrates

70 scattered hand-held sound meter readings (Q/N vs PC vs dBA) triangulated and interpolated into a smooth engineering contour map — no regular grid required. This is the standard technique for visualizing field measurement data, sensor networks, and survey results where samples are irregularly distributed across a 2D domain.

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Delaunay Triangulation vs Grid-Based Contour

ProEssentials offers two contour approaches in PesgoWpf. Choosing the right one depends on your data structure:

Method	Data Shape	Best For
ContourDelaunay	Irregular scatter of XY points	Field surveys, sensor grids, acoustic measurements, geographic data
ContourColors	Regular rectangular grid	Spectrograms, images, uniform simulation output

ContourDelaunay is the correct choice whenever your data points do not fall on a regular grid — the typical case for real-world measurement campaigns.

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ProEssentials Features Demonstrated

ContourDelaunay — The Plotting Method

Pesgo1.PePlot.Method = SGraphPlottingMethod.ContourDelaunay;

ContourDelaunay (enum value 25 in SGraphPlottingMethod) is a self-contained plotting method that:

1. Computes the Delaunay triangulation of all XY point positions
2. Interpolates Z (dBA) values across each triangle
3. Renders the result as a continuous filled contour surface

Data Model — XYZ Scatter, Not a Grid

Pesgo1.PeData.Subsets = 1;        // always 1 for Delaunay
Pesgo1.PeData.Points  = 70;       // number of scattered measurement points

Pesgo1.PeData.X[0, p] = fX;      // Q/N  — flow coefficient (horizontal)
Pesgo1.PeData.Y[0, p] = fY;      // PC   — pressure coefficient (vertical)
Pesgo1.PeData.Z[0, p] = fZ;      // dBA  — the quantity being contoured

Graph Annotations on Every Data Point

Pesgo1.PeAnnotation.Graph.X[p]    = fX;
Pesgo1.PeAnnotation.Graph.Y[p]    = fY;
Pesgo1.PeAnnotation.Graph.Type[p] = (int)GraphAnnotationType.SmallDotSolid;
Pesgo1.PeAnnotation.Graph.Text[p] = string.Format("{0:##0.0}", fZ);

Each of the 70 measurement locations is marked with a dot symbol and its dBA value as a text label — making individual readings visible on top of the interpolated surface. A named Pointer annotation marks a specific test spot.

Manual Z Range Control

Pesgo1.PeGrid.Configure.ManualScaleControlZ = ManualScaleControl.MinMax;
Pesgo1.PeGrid.Configure.ManualMinZ          = 80.0F;
Pesgo1.PeGrid.Configure.ManualMaxZ          = 102.0F;

Clamps the contour color scale to the known dBA measurement range. Prevents a single outlier from skewing the entire color ramp — critical for engineering contour maps where absolute scale reference matters.

Custom Contour Color Array

Pesgo1.PeColor.ContourColors.Clear(6);
Pesgo1.PeColor.ContourColors[0] = Color.FromArgb(255, 0,   0,   255); // blue
Pesgo1.PeColor.ContourColors[1] = Color.FromArgb(255, 17,  211, 214); // cyan
Pesgo1.PeColor.ContourColors[2] = Color.FromArgb(255, 0,   255, 0);   // green
Pesgo1.PeColor.ContourColors[3] = Color.FromArgb(255, 255, 255, 0);   // yellow
Pesgo1.PeColor.ContourColors[4] = Color.FromArgb(255, 245, 181, 5);   // orange
Pesgo1.PeColor.ContourColors[5] = Color.FromArgb(255, 255, 0,   0);   // red
Pesgo1.PeColor.ContourColors[6] = Color.FromArgb(255, 0,   55,  155); // dark blue

Pesgo1.PeColor.ContourColorBlends = 2;   // set BEFORE ContourColorSet
Pesgo1.PeColor.ContourColorAlpha  = 225;
Pesgo1.PeColor.ContourColorSet    = ContourColorSet.ContourColors;

ContourColorBlends must always be set before ContourColorSet.

PeCustomTrackingDataText Event — Custom Tooltip (WPF)

// Wire up in Loaded event handler:
Pesgo1.PeCustomTrackingDataText += Pesgo1_PeCustomTrackingDataText;

// Handler:
private void Pesgo1_PeCustomTrackingDataText(object sender,
    Gigasoft.ProEssentials.EventArg.CustomTrackingDataTextEventArgs e)
{
    double dX = Pesgo1.PeUserInterface.Cursor.CursorValueX;
    double dY = Pesgo1.PeUserInterface.Cursor.CursorValueY;

    e.TrackingText = string.Format(
        "Q/N:  {0:0.0000}\nPC:   {1:0.0000}\ndBA:  {2}",
        dX, dY, e.TrackingText);
}

TrackingCustomDataText = true activates this event. The handler reads the cursor's data-coordinate position and replaces the default tooltip with a formatted multi-line readout. e.TrackingText on entry already contains the interpolated Z value from the Delaunay mesh.

Monochrome Fallback

for (int s = 0; s < 30; s++)
    Pesgo1.PeColor.SubsetShades[s] = Color.FromArgb(255,
        (byte)(50 + (s * 2)), (byte)(50 + (s * 2)), (byte)(50 + (s * 2)));

When the chart is viewed or printed in monochrome mode, SubsetShades provides grayscale bands that replace the color contours.

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Data File

DelaunaySample.txt — 70 lines, space-delimited X Y Z per line.

• X — Q/N (flow coefficient)
• Y — PC (pressure coefficient)
• Z — dBA (sound level measurement)

Copied to the output directory automatically on build.

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Controls

Input	Action
Left-click drag	Zoom box
Right-click / z	Undo zoom
Mouse wheel	Horizontal + vertical zoom
Mouse drag	Pan
Right-click	Context menu — export, print, customize, annotations
Double-click	Customization dialog

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Prerequisites

• Visual Studio 2022
• .NET 8 SDK
• Internet connection for NuGet restore

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How to Run

1. Clone this repository
2. Open DelaunayTriangulation.sln in Visual Studio 2022
3. Build → Rebuild Solution (NuGet restore is automatic)
4. Press F5

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NuGet Package

References ProEssentials.Chart.Net80.x64.Wpf. Package restore is automatic on build.

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Related Examples

• WPF Heatmap Spectrogram — Grid-Based Contour
• WPF Quickstart — Simple Scientific Graph
• Financial OHLC — Trading Signals
• 3D Realtime Surface — ComputeShader
• All Examples — GigasoftInc on GitHub
• Full Evaluation Download
• gigasoft.com

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License

Example code is MIT licensed. ProEssentials requires a commercial license for continued use.