[vtkusers] Another question on vtkLookupTable..!

[rakesh patil]

Hi David,

It can be done by repeating colors as you say. But how do I identify the
number of table values? Because the values
10
20
30
40
50
60
80
100
200

is entered by user. and user may enter any value like,

10
20
30
35
40
45
70
90
100
200

In this case, number of table values will be more (i.e. @ interval of 5).
Well, I'll just give a try. Number of colors should remain same in either
case right? only number of table values will vary. Am I correct..??

Thanks

Regards
Rakesh Patil

On Tue, Feb 22, 2011 at 2:41 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Rakesh,
>
> You can't change the fact that the binsize is uniform.  But I don't
> understand why you don't just repeat the colors:
>
> 10     ==== (1.0, 0.0, 0.0)
> 20     ==== (1.0, 0.5, 0.0)
> 30     ==== (1.0, 1.0, 0.0)
> 40     ==== (0.5, 1.0, 0.0)
> 50     ==== (0.0, 1.0, 0.0)
> 60     ==== (0.0, 1.0, 0.5)
> 70     ==== (0.0, 1.0, 0.5)
> 80     ==== (0.0, 1.0, 1.0)
> 90     ==== (0.0, 1.0, 1.0)
> 100   ==== (0.0, 0.5, 1.0)
> 110   ==== (0.0, 0.0, 1.0)
> ... ditto for 120 to 190 ...
> 200   ==== (0.0, 0.0, 1.0)
>
>  - David
>
> On Tue, Feb 22, 2011 at 12:58 AM, rakesh patil
> <prakeshofficial at gmail.com> wrote:
> > Hey David,
> >
> > Thanks for that explanation. Now it's bit clear about how lookup table
> > works. But in my case, I guess, binsize is not uniform. Let me put it in
> > this form
> >
> > 10     ==== (1.0, 0.0, 0.0)
> > 20     ==== (1.0, 0.5, 0.0)
> > 30     ==== (1.0, 1.0, 0.0)
> > 40     ==== (0.5, 1.0, 0.0)
> > 50     ==== (0.0, 1.0, 0.0)
> > 60     ==== (0.0, 1.0, 0.5)
> > 80     ==== (0.0, 1.0, 1.0)
> > 100   ==== (0.0, 0.5, 1.0)
> > 200   ==== (0.0, 0.0, 1.0)
> >
> > in this case, bin size is not equal to (max-min)/n. I mean, lookup table
> > might calculate it like that. But If dont want in that way, then what
> > changes I have to do to implement? May be I am wrong in understanding the
> > meaning of binsize. Please correct me if I'm wrong.
> >
> > Thanks
> >
> > Regards
> > Rakesh Patil
> >
> > On Tue, Feb 22, 2011 at 11:58 AM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> >>
> >> Hi Rakesh,
> >>
> >> The way that the lookup table maps values to colors is as follows:
> >> If the Range of the table is set to [min,max] and the number of colors
> >> in the table is n, then the equation that maps a value "v" to an
> >> index "i" is:
> >>
> >>  i = floor((v - min)*n/(max - min))
> >>
> >> The bin size is uniform and equal to (max - min)/n.  Values in the
> >> range [min, min + binsize] go into the first bin (and values less than
> >> min also go into the first bin).
> >>
> >> Since the bins are uniform in size, you will need a table with 20 values
> >> and a binsize of 10, and some of the colors will have to be repeated.
> >> Use lut->SetTableRange(0.5, 200.5), where the ".5" is for rounding.
> >>
> >>  - David
> >>
> >>
> >> On Mon, Feb 21, 2011 at 10:35 PM, rakesh patil
> >> <prakeshofficial at gmail.com> wrote:
> >> > Hello,
> >> >
> >> > I have to display contours, for a given range, by mapping values to
> >> > colours.
> >> > i.e. Consider I need to display contours between 1 and 200.
> >> >
> >> > I use the lookuptable as follows
> >> >
> >> > vtkSmartPointer<vtkLookupTable> lut =
> >> > vtkSmartPointer<vtkLookupTable>::New();
> >> > lut->SetNumberOfTableValues(9);
> >> > lut->SetTableValue(0, 1.00, 0.00, 0.00);
> >> > lut->SetTableValue(1, 1.00, 0.50, 0.00);
> >> > lut->SetTableValue(2, 1.00, 1.00, 0.00);
> >> > lut->SetTableValue(3, 0.50, 1.00, 0.00);
> >> > lut->SetTableValue(4, 0.00, 1.00, 0.00);
> >> > lut->SetTableValue(5, 0.00, 1.00, 0.50);
> >> > lut->SetTableValue(6, 0.00, 1.00, 1.00);
> >> > lut->SetTableValue(7, 0.00, 0.50, 1.00);
> >> > lut->SetTableValue(8, 0.00, 0.00, 1.00);
> >> > lut->Build();
> >> > Now suppose I want the output like show below
> >> >
> >> > 01 - 10     ==== (1.0, 0.0, 0.0)
> >> > 11 - 20     ==== (1.0, 0.5, 0.0)
> >> > 21 - 30     ==== (1.0, 1.0, 0.0)
> >> > 31 - 40     ==== (0.5, 1.0, 0.0)
> >> > 41 - 50     ==== (0.0, 1.0, 0.0)
> >> > 51 - 60     ==== (0.0, 1.0, 0.5)
> >> > 61 - 80     ==== (0.0, 1.0, 1.0)
> >> > 81 - 100    ==== (0.0, 0.5, 1.0)
> >> > 101 - 200  ==== (0.0, 0.0, 1.0)
> >> >
> >> > How can this be done.?? So that the values supplied should be mapped
> to
> >> > the
> >> > corresponding colour and should be displayed.
> >> >
> >> > Thanks
> >> >
> >> > Regards
> >> > Rakesh Patil
> >
> >
>
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