Re: [opendx-users] Streamlines

[Frederick R. Phelan Jr.]

At 09:05 AM 4/6/01 -0600, you wrote:
>The grid should be part of your velocity data. How are your velocity
>vectors mapped in space? If you don't have them on a grid, this isn't
>going to work.
>
>If you need to specify your start position, in the Streamline cdb,
>enter [x y] for the start input with x and y as your start position.
>

Yes, I have a grid ... just a simple N x N mesh in this case. Since the previous message I figured out that I can enter points for START as so: {[0,0] [0,0.1] [0,0.2] etc.} and a streamline will indeed be drawn from every one of the specified points.

The question is how can I automatically pipe all the individual grid positions into the start box? I hate to have to retype things for every single different mesh. The data for START must either be in the form of a vector list or geometry field.

Fred

>
>>Thanks for your reply ...
>>
>>I know that streamlines should not look exactly like the glyphs per
>>se, but what I meant was that the shape of the streamlines does not
>>seem to correspond to the computed velocity field, and since the
>>velocity field looks good, I conclude that I am screwing up the DX
>>stuff!
>>
>>I think the problem is that I am not specifying the "START" data
>>component of the STREAMLINE module correctly. The default value for
>>this is "center of object" and given that, the one streamline I see
>>does make sense ... it starts at the center of the mesh, and
>>terminates at the boundary.
>>
>>Seems like I somehow need to give the STREAMLINE module the grid
>>positions and I am not sure how to do that ... Anyone got an idea???
>>I tried specifying "positions", but that did not work.
>>
>>Thanks,
>>Fred Phelan
>>
>>At 08:01 AM 4/6/01 -0400, you wrote:
>>>>Can DX render streamlines from 2-D velocity data?
>>>>
>>>>I am passing the velocity data through the sequence:
>>>>
>>>>{velocity} -> STREAMLINE -> AUTOCOLOR -> IMAGE
>>>>
>>>>But I get a very strange rendering that looks nothing like the
>>>>glyphs of the velocity field.
>>>>
>>>>Also tried:
>>>>
>>>>{velocity} -> STREAMLINE -> AUTOCOLOR -> ISOSURFACE -> IMAGE
>>>>
>>>>But that gave an error!
>>>>
>>>>Thanks,
>>  >>Fred Phelan
>>>
>>  >
>--
>.............................................................................
>David L. Thompson                          The University of Montana
>mailto:[EMAIL PROTECTED]                Computer Science Department
>http://www.cs.umt.edu/u/dthompsn          Missoula, MT  59812
>                                            Work Phone : (406)257-8530

---

Frederick R. Phelan Jr., Ph.D.
Multiphase Materials Group
Polymers Division
National Institute of Standards and Technology

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