Clipping Elevation surfaces -- Cutting planes

• To: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Subject: Clipping Elevation surfaces -- Cutting planes
• From: Mohamad jadi <mohamad@xxxxxxxx>
• Date: Fri, 07 May 1999 13:48:58 -0600

The plane-layer intersection lines could be useful too.  But since what we have
is a stack of flatfields of (x, y) --> z then "clipping" the layers by some
plane(s) could be a useful operation and visualization.  So the result of
clipping a layer by one or more planes would be a new layer which is like the
original layer but minus some part of it.

-- mohamad
LANL

Bill Hibbard wrote:

> Hi Mohamad and Ugo,
>
> > The idea is to be able to depict a movable plane that sweeps the
> > DEM and sends the data of the intersection curve to the 2D display.
>
> If the DEM is "FlatField elevation" with MathType ((x, y) -> z) then
> to make a vertical cutting plane, construct "Gridded2DSet cutting_set"
> with MathType Set(x, y) and manifold dimension = 1, whose samples
> lie along the line in the (x, y) plane that is the intersection of
> the (x, y) plane with the vertical cutting plane.  Then:
>
>   FlatField cut_elevation = (FlatField)
>     elevation.resample(cutting_set, Data.WEIGHTED_AVERAGE, Data.NO_ERRORS);
>
> and cut_elevation will be displayed in your 3-D DEM display as the
> curve that is the intersection of your DEM with the vertical cutting
> plane.  For your 2-D display, construct another RealType w that
> represents location along the line in the (x, y) plane and construct
> "Gridded1DSet dem2d_samples" with MathType Set(w) and whose samples are
> the w locations of the samples of cutting_set.  Then:
>
>   FunctionType dem2d_type = new FunctionType(w, z);
>   FlatField dem_2d = newFlatField(dem2d_type, dem2d_samples);
>   double[][] values = cut_elevation.getValues();
>   dem_2d.setSamples(values);
>
> Now you can display dem_2d in 2-D with the ScalarMaps:
>
>   ScalarMap(w, Display.XAxis);
>   ScalarMap(z, Display.YAxis);
>
> If your DEM display includes 3-D FlatFields [i.e., MathType
> ((x, y, z) -> attribute)] representing sub-surface data, then you can do
> something similar by defining a "Gridded3DSet cutting_plane" with MathType
> Set(x, y, z) and manifold dimension = 2, whose samples are a 2-D grid lying
> on the cutting plane.  Then resample the 3-D FlatFields to cutting_plane,
> etc.
>
> Cheers,
> Bill
> ----------------------------------------------------------
> Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
> hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
> http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • Re: Elevation surfaces -- Cutting planes
    • From: Bill Hibbard