| IDLgrPoly[line|gon] and cv_coord [message #33504] |
Tue, 07 January 2003 14:35  |
paul wisehart
Messages: 28
Registered: December 2002
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Junior Member |
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Hi,
Its me again w/the 3D spheres : )
I'm having trouble understanding the coordinate system
w/regards to the IDLgrPolyline (or Polygon) methods and 'orb's.
Here's an example:
;--------------------------------------------------
my_image = obj_new('IDLgrImage', earthImage)
my_orb = obj_new('orb', COLOR=[0, 255, 0], RADIUS=0.8, $
DENSITY=2, /TEX_COORDS, TEXTURE_MAP=oimage1,style=1,hide=0,/zero)
pt_radius = 1
pt1 = [0,0,pt_radius]
pt2 = [15,0,pt_radius]
sph_coord = [pt1,pt2]
rect_coord = CV_COORD(FROM_sphere=sph_coord,/to_rect)
my_poly = obj_new('idlgrpolyline',rect_coord,$
thick=10,color=[255,0,0])
my_model -> add, my_poly
my_model -> add, my_orb
xobjview, my_model
;--------------------------------------------------
My 'pt1' and 'pt2' are supposed to be lat/lon coordinates.(spherical)
I convert them to rectangular coordinates.
I've tried pt_radius values .4 -> 1.4 (or so)
I'm trying to draw a line on the surface of the sphere.
The lines I am getting are outside the sphere or not there.
I cannot figure out how the coordinate system works.
I am assuming that by leaving the radius constant my lines will
follow the curve of a sphere.
Whats the default coordinate range of an 'orb' object?
Where's [0,0,0]? At the center of the sphere?
Is the sphere in a 'frame' where [0,0,0] is a vertex?
I can't find any info on the coordinate systems used in object
graphics in the manual either. Maybe someone know's where to look?
(IDL 5.4 by the way)
THANKS!!!!
I'll try to stop bugging you after this one.
--
paul wisehart
wisehart <at> runbox <dot> com
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| Re: IDLgrPoly[line|gon] and cv_coord [message #33558 is a reply to message #33504] |
Wed, 08 January 2003 13:49  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Rick Towler (rtowler@u.washington.edu) writes:
> I can't argue that there doesn't exist a graphics library whose coordinate
> system is not rectangular, but openGL's is.
Yes, this is probably true. In any case, it makes sense. :-)
> Try defining an IDLgrPolygon
> with [angle, radius, z] values instead of [x,y,z]. I don't think you'll get
> what you were expecting.
No, I'm sure not. But what I had in mind was defining an FSC_Polygon.
I'm pretty sure I could make one of those that allowed you
to specify angle, radius and z value. But you are probably right
that I would eventually have to translate it back to OpenGL's
rectangular coordinate system.
I guess rotations would be the same thing. In *my* odd coordinate
system you could appear to rotate about (3.459, 78.452), but to
actually implement it in my code I'd have to translate it
to the origin to take advantage of OpenGl, then translate it
back to where it was suppose to be. Lot's of bother, to be sure.
No one would volunteer to do it, I'm sure of that. :-)
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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