Jiří Hnídek wrote: > Hi Christophe, > thanks for reply. > > Christophe Geuzaine píše v Pá 05. 12. 2008 v 13:56 +0100: >> Jir(í Hnídek wrote: >>> Hi, >>> I created small patch of GMSH source code. This patch is created from 2 >>> days old cvs source snapshot (I mentione this, because noticed lot of >>> new code in last cvs snapshot). This patch adds option to change minimal >>> arrow size. Hopefully, this screenshot describes more: >>> >>> http://dl.getdropbox.com/u/369894/GMSH_minimal_arrow_size.png >>> >>> Why is it useful for us? We try to do visualization of water flow in a >>> underground (simulation of poisoned water, simulation of >>> decontamination, etc). There are areas with large flow speed (rifts) and >>> very small flow speed (massif). Flows in massif are sometimes so small, >>> that are invisible with logarithmic value scale. This option could help >>> us see and understand processes in underground better :-). >>> >> Hi Jiri - Thanks for the patch. This could indeed be very interesting: >> we'll have a look. >> >> Another thing you could try is to select the "logarithmic" value scale >> mode. That's the mode we usually use when we visualizae vector fields >> with large variations. How does it work on your dataset? > > Logarithmic value scale works fine for some types of data set, but for > example in this case it doesn't work too good: > > Linear value scale: > http://dl.getdropbox.com/u/369894/Linear_vector_field.png > > Logarithmic value scale: > http://dl.getdropbox.com/u/369894/Logarithmic_vector_field.png > > Logarithmic value scale win minimal arrow size: > http://dl.getdropbox.com/u/369894/Logarithmic_vector_field_with_min_arrow_size.png > > Why logarithmic value scale does not work for us too good in this case? > It is influenced by code in function drawVectorArray(...): > > scale = opt->ArrowSize / l * log10(l / opt->TmpMin) / > log10(opt->TmpMax / opt->TmpMin); > > This returns zero values for vectors near to the smallest vector in a > vector field. Most of vectors in our vector fields are near to the > minimal vector, because flow in massif is small. Why are so small flows > so important for us? Because such flows are in large volumes and amount > of flowed water could be significant.
Indeed. We've just added a modified version of your patch. Let us know what you think... > >>> If you will find my patch interesting, then let me know, I can recreate >>> it against new cvs source snapshot. I will try to ask again. Do you have >>> any public cvs repository? This would help me very much. Are you >> Not public, but we create accounts for frequent contributors. > > Ok, I will try to convince you, that I deserve account :-). How many > patches should I send to be accepted as contributor? I'm Blender > developer and Blender developer community gives subversion write access > to developer, who contributed 3 good patches. Do you have similar > politic? No official politic: it just happens when it happens ;-) > >>> interested in any cooperation? I have some ideas to improve GMSH. What >> Of course! Don't hesitate to contact us with ideas, remarks, etc. > > I would like to focus at OpenGL. It seems you use OpenGL immediate mode > in many cases. I would like to rewrite it with OpenGL display lists or > vertex arrays. I know it isn't so easy in project like GMSH. We have > same problems in Blender. We still use OpenGL immediate mode, becuase > Blender has old design (should be rewritten in blender2.5 though). > Gmsh actually uses vertex arrays for pretty much everything (meshes and scalar datasetsets). But it still uses immediate mode for the geometry and for vector post-processing datasets. The geometry is not a problem; but getting vector datasets to use vertex arrays could be hugely beneficial... Can you imagine a way how one could do this? > BTW: I created wiki page (czech language) for my colleagues. They should > write there some ideas about improving GMSH: > > https://www.nti.tul.cz/wiki/WikiUser:Jiri.Hnidek/GMSH_Ideas > >> Cheers, >> >> Christophe > > Cheers, > > Jiri > > > ------------------------------------------------------------------------ > > _______________________________________________ > gmsh mailing list > [email protected] > http://www.geuz.org/mailman/listinfo/gmsh -- Prof. Christophe Geuzaine University of Liege, Electrical Engineering and Computer Science http://www.montefiore.ulg.ac.be/~geuzaine _______________________________________________ gmsh mailing list [email protected] http://www.geuz.org/mailman/listinfo/gmsh
