Gradient of 2D Mesh

[19kdc3]

Hi Marco,

I have a 2D mesh that exists in the XZ-plane and would like to find the gradient within/on the mesh, towards the outside/edge. The .operation("gradient") seems to only calculate normal to the mesh surface.

Alternatively, I've tried using .silhouette('2d') since it mentions returning a "new line mesh", but I can't seem to do any thing more once a silhouette is applied to the mesh.

Is there a way to use the gradient operation for this use case?

Thanks for the help!

[marcomusy]

hi, not sure if i understand the question (gradient of what scalar field? the distance from the boundary?), if so you can maybe compute it with mesh.distanceTo(silhuette) where silhuette=mesh.silhouette('2d')

[marcomusy]

..for the gradient:

from vedo import *

shape = load(dataurl+'timecourse1d.npy')[56]

msh = shape.tomesh(invert=1).smooth().lw(0)           

bnd = msh.boundaries().c('g5').lw(5)
msh.distanceTo(bnd)
msh.cmap('hot').addScalarBar()

gradd = msh.gradient()
arrs = Arrows2D(msh.points(), msh.points()-gradd*0.3)
arrs.z(0.01) # so the stay on top
arrs.c('white')

show(msh, bnd, arrs, bg='bb').close()

[19kdc3]

That looks great! From those pictures I believe that's what I'm looking for.

Unfortunately, when I try to run your code I get the error: "'Mesh' object has no attribute 'GetScalars'" for the line gradd = msh.gradient()

Do you have any suggestions?

[marcomusy]

oh, have you tried
pip install vedo -U

ps : careful about mesh and msh because you are importing with from vedo import *

[19kdc3]

I thought I had the most recent version, since I installed it recently, but I guess not recent enough!

Thanks so much for the help! I was able to achieve the desired results:

A small inconvenience is that the arrows are drawn on the wrong plane such that they appear to have "zero thickness" when viewed in the y-axis. Is there an easy way to correct that?

If I'd like to probe for values throughout the gradient (not necessarily at a node/vert location) does the method you provided allow for interpolation? or does it need to switch from a mesh to volume?

Again, thanks so much for the help! I really appreciate it.

[marcomusy]

Nice!
About arrows, just use the 3d version Arrows() instead.
About interpolation check out https://github.com/marcomusy/vedo/blob/master/examples/advanced/interpolateScalar4.py and the other of the serie.