Re: Problem imaging a matrix

Hi Bill,

Thanks for your reply. Your suggestions were very helpful in providing me with new avenues along which to search. Unfortunately, after implementing your suggestions things still didn't work out as I was expecting.

Upon performing the steps:
GraphicsModeControl dispGMC = (GraphicsModeControl) display.getGraphicsModeControl();
    dispGMC.setCurvedSize(1); // map texture onto full-res terrain
I get the same result as before (I get 5 equi-spaced peaks and 4 valleys).

Changing setCurvedSize to 0 results in 9 equi-spaced peaks and 8 valleys. I get the same results when I use the alternative setting:
    dispGMC.setTextureEnable(false);  // disable texture mapping
    //dispGMC.setCurvedSize(0); // map texture onto full-res terrain

I noticed that when I set the 1s along the alternative diagonal, i.e. (1, 9), (2, 8), (2, 7), (2, 6), etc), that the display becomes a ridge along the diagonal as I expect. This occurs when setCurvedSize is given a setting of both 1 and 0.

It seems as though the 2D interpolation for the display is occurring at double the spatial frequency of the domain that the data exists over. It also seems as though this interpolation has a presumed angular orientation. Can I have any control over these parameters? My domain is defined using:
    domain_set = new Linear2DSet(domain_tuple, 1.0, (double)NROWS, NROWS,
                                         1.0, (double)NCOLS, NCOLS);

Any further suggestions that you may have would be very helpful.

Thanks again.


Wallace George

At 07:57 AM 10/5/00 -0500, Bill Hibbard wrote:
Hi Wallace,

> I've been following through Ugo Taddei's VisAD Tutorial. In section 4.3 of
> the tutorial, it discusses an example where, among other things, a color
> and height mapped image of a matrix is obtained. I decided to substitute my
> own matrix and the resulting image didn't look like what I expected. So I
> decided to test things with an identity matrix instead. I expected to see a
> ridge along the diagonal. Instead I obtained a series of peaks (going to 1)
> and valleys (going to zero) along the diagonal. There are 5 peaks and 4
> valleys. I've obtained the same results with both Java3D 1.2.2 and 1.3.
> Interestingly, if I comment out the line which adds the altitude map to the
> display, the resulting flat display is appropriately color mapped along the
> diagonal as I would expect. So whatever "problem" I'm having seems to be
> only in the z-mapping.
> Are my assumptions about what I should expect correct? Any suggestions
> about what may be occurring would be greatly appreciated.

I order to speed up rendering, by default VisAD reduces the
resolution of terrain surfaces using texture mapping.  You
can disable this in two different ways:

  GraphicsModeControl mode = display.getGraphicsModeControl();
  mode.setTextureEnable(false);  // disable texture mapping


  GraphicsModeControl mode = display.getGraphicsModeControl();
  mode.setCurvedSize(1); // map texture onto full-res terrain

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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