Vortex shedding around a half-cylinder rendered by POV-Ray (pdf, high resolution png).

Here the POV-Ray arrow layer is produced from Gerris (gfs) output with the command

vfplot -v -w4i -m2/2/0.2 -s0.0002 -i250/4 -l0/1in \
    -d bvk.dom --cache 1024 -e0.1p --glyph triangle \
    --output-format povray -o vfplot.inc \
    --format gfs frame-2.0.gfs

producing vfplot.inc.

As in the PostScript version of this image, the vorticity is extracted from the gfs file to make a GMT grd file vort.grd but now this is used to make a png of the vorticity:

grdimage vort.grd -R-0.3/0.7/-0.3/0.3 -JX4i/2.4i \
    -Cpolar > vort.eps
convert -density 300 -trim vort.eps -rotate 90 vort.png

in the file vort.png. Then the following POV-Ray script uses this to colour the cone glyphs in the image.

#include "colors.inc"
#include "shapes.inc"

#declare CD = 130;
#declare MX = 144;
#declare MY = 86;

camera {
  location <1.3*MX, MY, -CD>
  look_at <MX, MY, 0>
}

light_source {
  <0, 0, -CD>
  color rgb 0.5
  parallel
  point_at <0, 0, 0>
}

light_source { <   0,   MY, -CD> color rgb 0.3 }
light_source { <2*MX,   MY, -CD> color rgb 0.3 }
light_source { <  MX, 2*MY, -CD> color rgb 0.4 }

background { color rgb 0.9 }

#declare vfplot_arrow_texture =
  texture {
    pigment {
      image_map {png "vort.png" once}
      scale <288, 173, 1>
    }
    finish {
      phong 0.5
    }
  };

#include "vfplot.inc"

object {
  intersection {
    Round_Cone_Merge(<85, 85, -10>, 35, <85, 85, 10>, 35, 1)
    plane { x, 85 }
  }
  pigment { color rgb 0.8 transmit 0.45 }
  finish {
    phong 0.5
  }
}

Details on vfplot POV-Ray output can be found here.