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"""Plot streamlines for the 2D field:
u(x,y) = -1 - x:^2 + y
v(x,y) = 1 + x - y:^2
"""
from vedo import Points, settings, show
from vedo.pyplot import streamplot
import numpy as np
settings.default_font = "DejavuSansMono"
# a grid with a vector field (U,V):
X, Y = np.mgrid[-5:5 :15j, -4:4 :15j]
U = -1 - X**2 + Y
V = 1 + X - Y**2
# optionally, pick some random points as seeds:
prob_pts = np.random.rand(200, 2)*8 - [4,4]
sp = streamplot(
X,Y,
U,V,
lw=2, # line width in pixel units
direction='forward', # 'both' or 'backward'
probes=prob_pts,
cmap='viridis',
)
sp.add_scalarbar()
pts = Points(prob_pts).ps(5).c('white')
show(sp, pts, __doc__, axes=1, bg='bb').close()
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