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Re: 3d device coordinates from a 3D polyline.... [message #81592 is a reply to message #81518]

Tue, 02 October 2012 09:46

George.millward
Messages: 26
Registered: October 2012

Junior Member

On Tuesday, October 2, 2012 3:22:12 AM UTC-6, alx wrote:
> Le lundi 1 octobre 2012 19:07:22 UTC+2, (inconnu) a écrit :
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>> On Monday, October 1, 2012 6:32:00 AM UTC-6, David Fanning wrote:
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>>>> I have am idlgrpolyline which I can rotate in a 3D view (with the trackball).
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>>>> I want to know the 2D coordinates of this line in the device (ie,the 2D the projection in the window). Can't figure it out.
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>>> I'm no expert in this area, but I think the 3D to 2D
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>>> conversions of the transformation matrix (which you
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>>> can recover from the trackball) are well known. You
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>>> can read the answer at the bottom of this article,
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>>> for example:
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>>> http://math.stackexchange.com/questions/336/why-are-3d-
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>>> transformation-matrices-4x4-instead-of-3x3
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>>> Cheers,
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>>> David
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>>> --
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>>> David Fanning, Ph.D.
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>>> Fanning Software Consulting, Inc.
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>>> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
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>>> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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>> Hmm,
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>> So there is nothing in the object graphics system like the 'CONVERT_COORD' routine ?
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>> George.
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> In Object Graphics and New Graphics you can use "[XYZ]COORD_CONV" and
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> "ConvertCoord" methods, respectively. The last one being quite similar to the "Convert_Coord" function in Direct Graphics.
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> Alain.

Alain,

Thanks for your help.......I'm not using new graphics - this is all object graphics. I've been trying to understand how [XYZ]COORD_CONV in object graphics relates to all of this - but it's somewhat confusing.
I understand how XCOORD_CONV and YCOORD_CONV are used to map a 2D line to 2D normalized space - but I'm wanting the same for 3D...

Cheers

George.

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[Message index]

		3d device coordinates from a 3D polyline.... By: George.millward on Fri, 28 September 2012 14:30
		Re: 3d device coordinates from a 3D polyline.... By: George.millward on Thu, 04 October 2012 09:23
		Re: 3d device coordinates from a 3D polyline.... By: Karl[1] on Thu, 04 October 2012 13:16
		Re: 3d device coordinates from a 3D polyline.... By: Karl[1] on Wed, 03 October 2012 13:29
		Re: 3d device coordinates from a 3D polyline.... By: Michael Galloy on Wed, 03 October 2012 07:49
		Re: 3d device coordinates from a 3D polyline.... By: Michael Galloy on Tue, 02 October 2012 14:32
		Re: 3d device coordinates from a 3D polyline.... By: Karl[1] on Tue, 02 October 2012 14:02
		Re: 3d device coordinates from a 3D polyline.... By: George.millward on Tue, 02 October 2012 09:46
		Re: 3d device coordinates from a 3D polyline.... By: George.millward on Thu, 04 October 2012 13:21

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