[SCM] Gerris Flow Solver branch, upstream, updated. b3aa46814a06c9cb2912790b23916ffb44f1f203

[Stephane Popinet]

The following commit has been merged in the upstream branch:
commit a5e93314f7bb921c7b30f4880c2e85d25800f7a6
Author: Stephane Popinet <s.popinet at niwa.co.nz>
Date:   Wed Jun 15 08:28:18 2005 +1000

    Added PPM animate question to FAQ
    
    darcs-hash:20050614222818-fbd8f-6860b2fdf0f5cf853a9a93b1616a9ae034975a88.gz

diff --git a/doc/faq/faq.tex b/doc/faq/faq.tex
index cdbef9a..41b62e2 100644
--- a/doc/faq/faq.tex
+++ b/doc/faq/faq.tex
@@ -599,6 +599,32 @@ simulation in the file {\tt simulation-sum}. This file can then be
 post-processed (using {\tt gfs2oogl} for example) to obtain averages,
 standard deviations etc\dots (along any curves you want of course).
 
+\subsubsection{Using animate, the sequence of images generated by OutputPPM looks weird, what's happening?}
+
+This is probably an artefact of the way the {\tt animate} command
+displays a series of PPM images. What happens is that {\tt OutputPPM}
+generates PPM images which are just big enough to contain all the data
+in your simulation e.g. if you use 7 levels of refinement and one box,
+{\tt OutputPPM} will generate images with $128\times 128$ pixels. If
+you use an adaptive resolution with a maximum level of 6, the size of
+the resulting image generated by {\tt OutputPPM} can be anything in
+$1\times 1$, $2\times 2$, $4\times 4$, $8\times 8$, $16\times
+16$, $32\times 32$, $64\times 64$ depending on the maximum number of
+levels necessary to verify your adaptation criterion. As a result,
+{\tt animate} can see a series of PPM images with a variable size, if
+you look carefully you will see that the weird patterns you see are
+smaller-size images of your simulation, displayed in the top-left
+corner of the initial image. What {\tt animate} should really do is blank
+out the previous larger image before displaying the smaller image, to
+make the difference in size clear.
+
+The solution is simple, you can set the size of the images generated by {\tt OutputPPM} using:
+\begin{verbatim}
+OutputPPM { step = 0.05 } tracer.ppm { v = T maxlevel = 6 }
+\end{verbatim}
+which will result in PPM images of size $64\times 64$, independently
+of the maximum level of refinement in the simulation.
+
 \subsubsection{Why create a new visualisation tool like 
 GfsView? Can't you use existing tools like Mayavi/VTK, OpenDX etc\dots?}
 

-- 
Gerris Flow Solver