| Re: plotting on a sphere [message #31399] |
Mon, 08 July 2002 14:32  |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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"Chris O'Dell" <odell@cmb.physics.wisc.edu> wrote in message
news:3D29BB6F.10405@cmb.physics.wisc.edu...
> Thanks to Mark and Dick Jackson! You both effectively gave me the
> same answer, and i used it and it works. Of course now i am
> required to learn object graphics somewhat -- like how do I get a
> title and a color bar on the "XOBJVIEW" screen?
To display more than one graphics atom in XOBJVIEW, you can collect
the references to those atoms in an array & pass that to XOBJVIEW.
For the title you can use an IDLgrText object. For the colour bar you
can use an IDLgrColorbar (though I've always found the IDLgrColorbar's
facilities for positioning rather clumsy).
Another tip: XOBJVIEW does not destroy the objects passed to it, so
you have to do that yourself (*after* the XOBJVIEW application has
been closed). In an interactive session you may have lost the object
references so you can use HEAP_GC.
But XOBJVIEW is rather limited and not extensible. If you want to go
further with object graphics I suggest you do one or both of two
things:
- Check out David Fanning's WWW site at http://www.dfanning.com/ and
look at his object graphics programs. FSC_SURFACE is a good place to
start.
- If you have IDL 5.5, download my Motley library from
ftp://ftp.niwa.cri.nz/incoming/m.hadfield/, copy all the files to a
directory on your IDL path, run the setup routine MGH_MOTLEY, then
run and look at some of the example routines like
MGH_EXAMPLE_SURFACE.
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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| Re: plotting on a sphere [message #31402 is a reply to message #31399] |
Mon, 08 July 2002 09:18  |
Christopher W. O'Dell
Messages: 20
Registered: February 2001
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Junior Member |
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Thanks to Mark and Dick Jackson!
You both effectively gave me the same answer, and i used it and it
works. Of course now i am required to learn object graphics somewhat --
like how do I get a title and a color bar on the "XOBJVIEW" screen?
But the basics work great!
Cheers,
Chris
Mark Hadfield wrote:
> "Chris O'Dell" <odell@cmb.physics.wisc.edu> wrote in message
> news:3D260AC8.3050406@cmb.physics.wisc.edu...
>
>
>> I am new to 3D graphing in IDL. I would like to plot various
>> scalar fields on the surface of a sphere, displayed in 3D using
>> color contours. Ideally, I would be able to then use my mouse to
>> rotate the sphere to different orientations.
>>
>
> If you want 3D with rotations then you want object graphics.
>
> To create a sphere in object graphics, you use MESH_OBJ to create a list of
> vertex positions and a connectivity list (i.e. a list specifying which
> vertices have to be connected to draw the shape). Then you feed these to an
> IDLgrPolygon object. Here's an example that creates & displays a
> plain-coloured sphere:
>
> pro sphere_example
> compile_opt IDL2
> if n_elements(n_lon) eq 0 then n_lon = 20
> if n_elements(n_lat) eq 0 then n_lat = 20
> mesh_obj, 4, vert, conn, replicate(1, n_lon, n_lat)
> help, vert, conn
> sphere = obj_new('IDLgrPolygon', DATA=vert, POLY=conn, COLOR=[0,0,255],
> STYLE=2)
> xobjview, sphere
> end
>
> To give the sphere a non-uniform colour you use the IDLgrPolygon's
> VERT_COLORS property. You will see that the above example creates a mesh
> with 400 vertices. The X, Y & Z positions of the vertices are held in the
> columns of a [3,400] floating-point array. The VERT_COLORS array should be a
> [3,400] byte array, with the columns corresponding to red, green and blue
> respectively. Into this you need to load the color at each vertex, expressed
> as a function of the X, Y and Z position at that vertex.
>
> --
> Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
> m.hadfield@niwa.co.nz
> National Institute for Water and Atmospheric Research (NIWA)
>
>
>
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| Re: plotting on a sphere [message #31408 is a reply to message #31402] |
Sun, 07 July 2002 15:19 |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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"Chris O'Dell" <odell@cmb.physics.wisc.edu> wrote in message
news:3D260AC8.3050406@cmb.physics.wisc.edu...
> I am new to 3D graphing in IDL. I would like to plot various
> scalar fields on the surface of a sphere, displayed in 3D using
> color contours. Ideally, I would be able to then use my mouse to
> rotate the sphere to different orientations.
If you want 3D with rotations then you want object graphics.
To create a sphere in object graphics, you use MESH_OBJ to create a list of
vertex positions and a connectivity list (i.e. a list specifying which
vertices have to be connected to draw the shape). Then you feed these to an
IDLgrPolygon object. Here's an example that creates & displays a
plain-coloured sphere:
pro sphere_example
compile_opt IDL2
if n_elements(n_lon) eq 0 then n_lon = 20
if n_elements(n_lat) eq 0 then n_lat = 20
mesh_obj, 4, vert, conn, replicate(1, n_lon, n_lat)
help, vert, conn
sphere = obj_new('IDLgrPolygon', DATA=vert, POLY=conn, COLOR=[0,0,255],
STYLE=2)
xobjview, sphere
end
To give the sphere a non-uniform colour you use the IDLgrPolygon's
VERT_COLORS property. You will see that the above example creates a mesh
with 400 vertices. The X, Y & Z positions of the vertices are held in the
columns of a [3,400] floating-point array. The VERT_COLORS array should be a
[3,400] byte array, with the columns corresponding to red, green and blue
respectively. Into this you need to load the color at each vertex, expressed
as a function of the X, Y and Z position at that vertex.
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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| Re: plotting on a sphere [message #31437 is a reply to message #31399] |
Thu, 11 July 2002 19:09 |
Paul Sorenson
Messages: 48
Registered: May 2002
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Member |
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"Mark Hadfield" <m.hadfield@niwa.co.nz> wrote in message
>
> But XOBJVIEW is rather limited and not extensible.
Actually, XOBJVIEW is a widget object, or more accurately it is a top level
base with a widget object inside of it. Because it is object oriented, all
of the usual OOP techniques to extend code can be applied. You could
probably customize the object's behavior by deriving a new class to suit
your needs. Or you could include that object in a program of your own.
The underlying design of XOBJVIEW is a variation of the Bridge design
pattern from the Gamma, et al book "Design Patterns." As applied to
XOBJVIEW, the pattern separates the GUI widgets that you see on the screen
from the object graphics classes that implement their behavior, thus
separating interface from implementation.
This is useful if you want to create your own widget "skin" for XOBJVIEW's
features. For example, you could probably write your own widget interface
in Visual Basic and use the object graphics classes that underly XOBJVIEW
for the implementation/behavior of those widgets via ActiveX. (You may need
to write some simple wrapper classes to get this done, but I suspect it
would not be hard to do.)
-Paul Sorenson
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