Re: display areas

• To: David Selleron <david.selleron@xxxxxxxxxx>
• Subject: Re: display areas
• From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Date: Tue, 29 Oct 2002 10:30:50 -0600

David Selleron wrote:
> 
> Hello,
> 
> How can I paint cells defined with 4 points ( An area used one color) ?
> 
> p(10,10)--------------p(11,10)--------p(12,10)
> |                     |                |
> |    color 1          |    color 2     |
> |                     |                |
> p(10,09)--------------p(11,09)--------p(12,09)
> 
> 
> if I associate a color to a point with function (x,y) -> (r,g,b),
> the differents points are not on intersection of the color area.
> When I use these points to draw a regular or scottich grid and color area, 
> the grid doesn't
> defined the border of the differentes color area.
> 
> 
> p(10,10)-----"---------p(11,10)--"--------p(12,10)
> |            "         |         "           |
> |  color 1   " color 2 | color 2 "  color 3  |
> |            "         |         "           |
> p(10,09)-----"---------p(11,09)--"--------p(12,09)

You are right. The exact locations of the borders between
texture pixels is complex and includes calculations inside
of Java3D. Furthermore, for a nrows x ncols grid VisAD will
make a texture of nrows x ncols pixels, whereas the grid
has (nrows - 1) x (ncols - 1) grid interiors.

To get exact control over grid box locations, you need to
do something like what I described in an earlier email:

  Another approach is to use something similar to the
  approach in visad/examples/DelaunayTest.java, except that
  you will construct a FieldImpl with MathType like:

    (index -> ((x, y) -> (red, green, blue)))

  Where the FlatFields ((x, y) -> (red, green, blue)) have
  Gridded2DSet domains, each with only 4 = 2 x 2 points (one
  for each grid cell). The ScalarMaps are the usual:

    x -> XAxis
    y -> YAxis
    z -> ZAxis
    red -> Red
    green -> Green
    blue -> Blue

But if you have a million grid boxes (as you say below) this
will use a lot of memory.

You have an unusual problem, combining:

1. the need for solid coloring of grid box interiors
2. irregular spacing of grid points
3. a million points

I suspect the answer may need to be a custom DataRenderer,
which gives you precise control over how you use Java3D.
There is a tutorial on DataRenderers at:

  http://www.ssec.wisc.edu/~billh/dr_tutorial.html

>  Bill Hibbard said in another email :
> 
> > This method in visad/DelaunayCustom.java:
> >
> >    public static Irregular2DSet fill(Gridded2DSet set)
> >
> >will return an Irregular2DSet for the interior of the region
> >surrounded by set, assuming it is a Gridded2DSet with manifold
> >dimension = 1 that does not self-interset. Note 'fill' connects
> >the first and last points of set to make a closed boundary.
> >
> >Then link the Irregular2DSet to your Display, passing an array of
> >ConstantMaps to addReference() to define the color.
> 
> If I have 3 Aeras, I have 3 Irregular2DSet ???
> How link an Irregular2DSet to a color ???
> 
> I have 1 million of areas, I can't used one Irregular2DSet for each area.
> I have only Scottich grid, have you an optimized method to draw grid and
> color area of the grid???

This answer that I sent to another user is not relevant to
your problem with scotch grids. But the combination of
irregular locations and large grid sizes is trouble with
both IrregularSets and your scotch grids.

Good luck,
Bill

• Follow-Ups:
  • Changing the orientation of a 3D display
    • From: John Osborne

• References:
  • display areas
    • From: David Selleron