Thursday, February 21, 2013

Rotatable 3D surface plot

Yesterday a customer asked me how to create a quick and dirty solution for displaying a rotatable three dimensional surface (using ChartPack). Here's the solution to it (for sake of clarity I use predefined data stored in the 12 by 14 array "Data"):
  1. Put the TPlot3D component on a form
  2. In the OnShow event add the following code:
        // suppress any redraw during the
        // construction of the plot
    P3d.SuppressPaint := true; 
        // adjust the data grid of the component 
        // fill the data grid
    for i:=1 to 14 do
      for j:=1 to 12 do
        P3d.GridMat[i,j] := Data[i,j];  
        // set the scales of the axes
        // this triggers a repaint
    P3d.SuppressPaint := false;    
  3. In the object inspector set the color model ("ColorCodingMode") to "cmThreeColors", the range of colors to a range of 0 to 35 (properties "ColorScaleLow" and "ColorScaleHigh"), and of course, the pivot colors ("ColorLow", "ColorMid", and "ColorHigh") according to your requirements.
As a small refinement I added a scrollbar which allows to adjust the property "ColorScaleHigh". Following is a screen shot of the mini demo:

You can download the sample program written for Delphi XE3 from here. The ZIP file contains the sources and the corresponding executable for Windows. In order to rotate the 3D plot simply click into the chart and drag the mouse holding the left mouse button down.