CGAL users discussion list

[Abdelkrim Mebarki <>]

Hi Dmyan,

The density of the placement is defined according to the minimal distance separating each two streamlines, but the resolution of the vector field is defined by the user. The vector fields prvided with the demo are synthetic fields, defined on a regular grid (nxn). This grid is overlaid on a spatial image to render the placement, the dimension of this image defines the final resolution of the placement.
In the demos I used a 512x512 image, so the resolution depends on this, and the field size (the size of the grid that defines the field).

dmyan wrote:

Dear Abdelkrim,

    I have another question about stream_line_2. Does the current implementation consider the density of the vector field? I only find the interface to get density of a point in the field, but which returns a constant value 1.0.

    Thanks!

 

best regards

 

dmyan

----- Original Message -----

From:

To:

Sent: Friday, November 16, 2007 12:25 AM

Subject: Re: [cgal-discuss] A question about streamline demo of CGAL 3.3

Hi,

The right result is shown in the first figure (The result that the package should produce using the default parameters). The web demo uses an old and modified version of the package, but produces the correct results.

In fact, there is a bug in the current version about the creterion used to stop the integration of the streamlines, precisely when the length of new introduced segment is checked (the threshold is very large, and must be reduced) ; This causes the premature end of the streamlines. This problem doesn't occur in the web demo because the short streamlines are deleted.

Attached is the fixed version, it will be in the next release.

dmyan wrote:

Dear CGAL users,

 

    I meet a problem when I run the demo Stream_lines_2.

 

    I found a demo program for stream lines at : http://www-sop.inria.fr/geometrica/team/Abdelkrim.Mebarki/Streamlines.html

The data file "10.vec" is used as input and the result is "result2.jpg" in attachment.

 

    I also run the demo Stream_lines_2 of CGAL3.3 and use the same vector filed as input, but the output is different from the previous demo. The result image is "result1.jpg" in attachment. 

 

    Did anyone meet the same problem as mine? Thanks very much!

 

Best regards

 

dmyan

--

Abdelkrim Mebarki.
Geometrica Project-team, I.N.R.I.A. Sophia Antipolis,
2004 route des Lucioles,
BP 93, 06902 Sophia Antipolis - FRANCE
Tel : (+33)(0)4 92 38 50 36
Fax : (+33)(0)4 97 15 53 95
http://www-sop.inria.fr/geometrica/team/Abdelkrim.Mebarki/index.htm