TContourplot hang when all YValues =0

[Werner]

Hi,

I use the last TChart V8.05 / D2007 ( but the same is with V8.03, V8.04).
If I fill the Tcontourplot with YValues all the same values ( for example 0 or 0.2) the program hangs.

Can you please help me, I have to deliver the program next week !!
A test program is attached.
Please press the load button and select the DADMIX.01Z file. Oberve that the program hangs if you switch to contour via the tabsheet.

with best regards

Werner

[Yeray]

Hi Werner,

Considering what is explained at teechart help for this series:

Description
Calculates and displays "isolines" from a custom array of XYZ points.

The number of contour levels can be specified from 1 to 250.
To see a visual representation of this Series type, go to the TeeChart User Guide.

The Surface's UseColorRange and UsePalette properties also apply to contour series.

Each contour Level can be coloured using a range (ie: from blue to white) or a "Palette", which can be customized for specific value intervals (ie: red from 100 to 200, green from 201 to 400 ). Same as with TSurfaceSeries.

Contour points can be assigned to a Surface and vice-versa:

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Series1.AssignValues( Series2 );

Each Level can be colored using a different color by doing:

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ContourSeries1.ColorEachPoint := True;

Levels can be displayed at custom "Y" vertical positions:

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ContourSeries1.YPosition := 123;

Each Level can display at it's own Level "Y" position by setting this property:

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ContourSeries1.YPositionLevel := True;

The ContourSeries, by default, shows at the Legend one item for each corresponding Contour "Level". The Contour Series has an event OnGetLevel which can be used to override each automatic Level Value and Color:

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procedure TForm1.Series1GetLevel(Sender: TContourSeries;
  LevelIndex: Integer; var Value: Double; var Color: TColor);
begin
  Value:=LevelIndex*100.0;
  if Value<500 then Color:=clBlue
               else Color:=clRed;
end;

The LevelIndex parameter specifies each contour level, from 0 to NumLevels-1.

*Note

ContourSeries1.MaxYValue and MinYValue refer to Contour Y values.
Since version 5, this depends on the 2D / 3D setting.
When the Chart is in 2D mode (Chart1.View3D:=False) then Contour MaxYValue and MinYValue methods return the Z values minimum and maximum values.

In 3D mode, the behaviour is the same as in version 4 (they refer to Contour Y values).

To remain independent on the above issue, you should use Contour.YValues.MaxValue and Contour.YValues.MinValue properties.

And also looking at this explanation from Narcis, I cant' see the sense of having a contour series with the same value for all the Y values. The contour series seems to need different YValues to define the levels.

[Werner]

Dear Yeray,

sorry , but I disagree completely. The data are sampled from a detector machine and therefore it could be happen, that all y-values have the same value. So you can't say to the user 'I cant' see the sense of having a contour series with the same value for all the Y values'. The program hangs, that is the fact.

Indeed, the problem is the calculation of the levels and your software guys have to have a look to the bounds of ranges that could be happen. If all y-values are the same value the following line in the teesurfa.pas (Procedure TContourSeries.CreateAutoLevels;) get the result of tmp= '0'

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tmp:=MandatoryValueList.Range/Max(1,NumLevels-1);

This value gets a problem in the following algorithm.

I have give you enough information, even a sample project (spendig my weekend to do this) to fix this bug, so please do it !

best regards
Werner

[Yeray]

Hi Werner,

My apologies if I looked immovable. The problem is that I'm still not able to understand how would you expect TeeChart to draw that situation. Maybe I'll understand better the expected result if you could attach also a picture showing it.

[Werner]

Hi Yeray,

the major problem is the program hang, if all y-values have the same value. Please compile my sample project, load the file as I described and see what happen.

Meanwhile I have fixed the problem, but I am not sure if it works in any cases, so please have a look at it.

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Procedure TContourSeries.CreateAutoLevels;
......
   tmp:=MandatoryValueList.Range/Max(1,NumLevels-1); // v8 changed to include max value
      if tmp=0 then tmp:=1;           //wdu

      tmpMin:=MandatoryValueList.MinValue;

      for t:=0 to NumLevels-1 do
      begin
        tmpUpTo:=tmpMin+tmp*(t+1); //wdu

I have attached the picture showing in the case of all y-values have the same value;

With best regards
Werner

[Yeray]

Hi Werner,

Excuse me again. For some reason I can't see, the first time I ran your application (and tried for several times) I got always a series without data. Then I guessed that there should be some problem in your loading file and that made me to think that the real problem was the "meaning" of the contour series and not a real hang.

Once retested your application and reproduced the hang, I've reduced the problem into a simpler example:

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procedure TForm1.FormCreate(Sender: TObject);
var x, z, index: Integer;
begin
  for x := 0 to 39 do
    for z := 0 to 39 do
      series1.AddXYZ(x,1,z)
end;

Note that the program finishes after about 5~10 seconds and there are only 1600 points. And I also could see that your patch seems to solve this really bad performance issue.

Finally, I'd like you to know that I've added this to the wish list to be fixed as soon as possible (TV52014344).