[GRASS-user] velocity flowlines

[Ken Mankoff]

Dear GRASS List,

I have a vx and vy velocity vector and I am trying to draw velocity flowlines, instead of just vector arrows. r3.flow [1] appears to have this functionality, but I'm trying to do this in 2D not 3D. I haven't been able to find the code to do this.

Trying 3D, I've tried to adapt the example:

r3.flow vector_field=vx,vy,vz flowline=gw_flowlines skip=5,5,2 direction=both

with my 2D data by:

r.mapcalc "vz = 0" --o
r.to.rast3 input=vx output=vx3 --o
r.to.rast3 input=vy output=vy3 --o
r.to.rast3 input=vz output=vz3 --o

r3.flow vector_field=vx3,vy3,vz3 flowline=flowlines direction=both --o
d.vect flowlines

But the 3D view crashes both on OS X and Linux using GRASS 7.4.0.

Thanks for any help with this,

  -k.

[1] https://grass.osgeo.org/grass74/manuals/r3.flow.html