Dear Gael,
thank you for your fast answer.
I manipulated the colormap, as you see below, but I am not sure it
does what I wanted, because I do not understand exactly how the LUT works.
I expected a smoother transition in the example below. This does not happens,
since
the value v in hsv is constant 1.
We can also compute the color of each computed point.
Is there an efficient way to plot only the points with their associated colors?
This will not look as good as mesh or surf, but it could be a start.
Another approach would be if
lut: [0,1] x [0,1] x [0,1] x [0,1] -> R x G x B x A
instead of
lut: [0,1] -> R x G x B x A
scalar |-> (r,b,g,alpha)
would be available, or even better,
mesh(..., scalar1=?, scalar2=?, scalar3=?, scalar4=?)
Any further ideas?
Thanks,
Vasile
from numpy import linspace, pi, exp, angle, squeeze, zeros
from matplotlib.colors import hsv_to_rgb
from enthought.mayavi import mlab
# 1) create a colormap which do what I think it should do:
def compute_color_map(): # B. Thaller like convention
k = linspace(-pi, pi, 256, endpoint=True)
#unitcircle = exp(1.0j*k)
#hsv_colors = zeros((1, unitcircle.shape[0], 3))
#hsv_colors[:,:, 0] = 0.5*(pi+angle(unitcircle))/pi
hsv_colors = zeros((1, k.shape[0], 3))
hsv_colors[:,:, 0] = 0.5*(pi+k)/pi
hsv_colors[:,:, 1] = 1.0
hsv_colors[:,:, 2] = 1.0
rgb_colors = hsv_to_rgb(hsv_colors)
color_map = 255*squeeze(rgb_colors)
return color_map
# 2) define the ploting function
def surfCF(gridx, gridy, phase, modulus, colormap=None):
"""Plot the modulus of a complex valued function $f:R^2 -> C$ together with
its phase in a color coded fashion.
@param grid: The grid nodes of the real domain R
@param phase: The phase of the complex domain result f(grid)
@param modulus: The modulus of the complex domain result f(grid)
@keyword colormap: The colormap to use, if none is given, compute the
'default' QM colormap.
"""
if colormap is None:
colormap = compute_color_map()
mesh = mlab.mesh(gridx, gridy, modulus, scalars=phase, vmin=-pi, vmax=pi)
# Set the custom color map
lut = mesh.module_manager.scalar_lut_manager.lut.table.to_array()
lut[:,0] = colormap[:,0]
lut[:,1] = colormap[:,1]
lut[:,2] = colormap[:,2]
mesh.module_manager.scalar_lut_manager.lut.table = lut
mlab.draw()
return mesh
# 3) then test it
if __name__ == "__main__":
from numpy import real, imag, conj, abs, mgrid
x, y = mgrid[-2:2:0.05, -2:2:0.05]
u = x*exp(-0.25*x**2)
v = y*exp(-0.25*y**2)
z = u*v
surfCF(x, y, angle(z), abs(z)**2)
________________________________________
From: Gael Varoquaux [gael.varoqu...@normalesup.org]
Sent: Thursday, June 09, 2011 7:43 AM
To: enthought-...@enthought.com
Cc: mayavi-users@lists.sourceforge.net
Subject: Re: [MayaVi-users] [Enthought-Dev] complex valued function with
"QM-standard" color convention?
On Wed, Jun 08, 2011 at 12:04:38PM +0000, Gradinaru Vasile Catrinel wrote:
> is that a map is defined with the help of the HLS color system
> (hue-lightness-saturation):
> - the hue of the color is given by angle(z)
> - the lightness is given by absolute value of z (0 is white)
> - the saturation is always maximal.
> In case of complex functions depending on only one variable, I was able
> to implement the same idea: just define the hsv_colors with this
> convention (well, in 1D is the lightness also maximal) and convert them
> to rgb_colors that we feed to the matplotlib routines, see below.
> How should I implement this with mayavi2?
Having a 2D colormap is not currently supported in Mayavi. If you want to
define your own 1D colormap (that can then be called 'LUT' for Look Up
Table), you can insert a pre-computed table, as can be seen in the
following example:
http://code.enthought.com/projects/mayavi/docs/development/html/mayavi/auto/example_custom_colormap.html
Hope this helps,
Gaël
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