DPlot

Posted: **Mon Aug 24, 2009 9:54 am**

I have a problem with 3D surface display.
My application is a Win32 program . The surface is defined as a 2D matrix with the size of Hcell-by-Vcell The surface height is defined as the value of the matrix elements, the x and y coordinates as the indecies of the matrix elements.
The matrix is stored in a double precision linear array Surf3d with the size of (Hcell+1)*(Vcell+1)
The surface values are arranged in the linear array as:

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					for (r=0;r<Vcell;r++) { // rows
						for (c=0;c<Hcell;c++) { // columns
							i = r*Hcell + c;
							Surf3d[i] = (double)rec[i];
						}
					}

rec are the experimentally measured surface data.
When I save the Surf3d array and display in Excel using Excel's native surface plot I see a completely acceptable surface.

I my program I try to display using

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                /* Initialize DPLOT structure to 0's: */
                memset(&DPlot,0,sizeof(DPlot));

                /* Fill in members of DPLOT structure */
                DPlot.Version    = DPLOT_DDE_VERSION;
                DPlot.hwnd       = (DWORD)hDlg;
                DPlot.DataFormat  = DATA_3D;
                DPlot.MaxCurves  = Hcell;
                DPlot.MaxPoints  = Vcell;
                DPlot.NumCurves  = 1;
                DPlot.Scale      = SCALE_LINEARX_LINEARY;
                strcpy(DPlot.Title[0],"The surface");
                strcpy(DPlot.XAxis,"X");
                strcpy(DPlot.YAxis,"Y");

                Lighting = 0;
                GetDlgItemText(hDlg,IDC_XRANGEEDIT,szText,sizeof(szText));
                xhi = atof(szText);
                GetDlgItemText(hDlg,IDC_YRANGEEDIT,szText,sizeof(szText));
                yhi = atof(szText);
                GetDlgItemText(hDlg,IDC_ZLORANGEEDIT,szText,sizeof(szText));
                zlo = atof(szText);
                GetDlgItemText(hDlg,IDC_ZHIRANGEEDIT,szText,sizeof(szText));
                zhi = atof(szText);
                xlo = 0.0; ylo=0.0;

                //if(Is3DView)
                sprintf_s(szExec, 1024,"[Caption(\"Heatbump plot\")]"
                          "[Contour3D(1)][ContourView(%d,20)][ContourLighting(%d,0.05)]", (int)angle, Lighting);

                sprintf_s(line, 1000, "[ContourGrid(0)][ContourAxes(1)][ContourMethod(0)][ContourLevels(20,%.3f, %.3f)]"
                          "[ContourScales(1,1,%d)][ManualScale(0,0,%.3f, %.3f,%.3f,%.3f)]"
                          "[FontPoints(1,8)][FontPoints(2,12)][FontPoints(3,12)]"
                          "[FontPoints(4,10)][FontPoints(5,10)][FontPoints(6,8)][FontPoints(8,10)]"
                          "[ZAxisLabel(\"Height\")][DocMaximize()]", MinRec, MaxRec, 5, xhi, yhi, zlo, zhi);

                strcat(szExec, line);


                if (hbmp) {
                    DeleteObject(hbmp);
                    hbmp = 0;
                }
                if (DocNum) dPlot_Command(DocNum, "[FileClose()]");
				DocNum = dPlot_Plot8(&DPlot, extents, Surf3d, szExec);
                if (DocNum) {
                    SetBitmapToFrame();
                    Is3D = 1;
                }
                free(z);

The Surface shown by dplot is very different from what I see from the Excel display:
The surface I am supposed to see in dplot is an inclined plane (as it show up in Excel surface plot) but with the dplot it looks like a plane surface with a warp aling the (i,i) line.

Any idea what could cause this defect?
Peter

Posted: **Mon Aug 24, 2009 11:53 am**

I wanted to attach a word doc with the two plots - I don't know how....
Peter

Posted: **Mon Aug 24, 2009 1:16 pm**

No attachments here, sorry. You're welcome to send files to support@dplot.com if you think it is necessary after this.

It looks to me like your loop limits and the calculation of i aren't correct, should be:

Code: Select all

for (r=0;r<Vcell+1;r++) { // rows 
    for (c=0;c<Hcell+1;c++) { // columns 
        i = r*(Hcell+1) + c; 
        Surf3d[i] = (double)rec[i]; 
    } 
}

Posted: **Mon Aug 24, 2009 1:54 pm**

DPlotAdmin wrote:No attachments here, sorry. You're welcome to send files to support@dplot.com if you think it is necessary after this.

It looks to me like your loop limits and the calculation of i aren't correct, should be:
Code: Select all
for (r=0;r<Vcell+1;r++) { // rows 
    for (c=0;c<Hcell+1;c++) { // columns 
        i = r*(Hcell+1) + c; 
        Surf3d[i] = (double)rec[i]; 
    } 
} 

David, I don't quite get it:
The double-loop in your code snippet implies that the array has a dimension of Hcell+1 by Vcell+1.
In reality there are Hcell elements horizonally and Vcell elements vertically.
Peter

Posted: **Mon Aug 24, 2009 2:00 pm**

OK, in that case this:

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DPlot.MaxCurves  = Hcell;
DPlot.MaxPoints  = Vcell;

should be

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DPlot.MaxCurves  = Hcell-1;
DPlot.MaxPoints  = Vcell-1;

And I probably need to do a better job of explaining this in the example source. Those are the number of rectangular grid cells in each direction (1 less than the number of points).

DPlot

Problem with Surface plot

Problem with Surface plot