"""
This example uses the isosurface function to convert a scalar field
(a hydrogen orbital) into a mesh for 3D display.
"""

import numpy as np

import pyqtgraph as pg
import pyqtgraph.opengl as gl

app = pg.mkQApp("GLIsosurface Example")
w = gl.GLViewWidget()
w.show()
w.setWindowTitle('pyqtgraph example: GLIsosurface')

w.setCameraPosition(distance=40)

g = gl.GLGridItem()
g.scale(2,2,1)
w.addItem(g)

## Define a scalar field from which we will generate an isosurface
def psi(i, j, k, offset=(25, 25, 50)):
    x = i-offset[0]
    y = j-offset[1]
    z = k-offset[2]
    th = np.arctan2(z, np.hypot(x, y))
    r = np.sqrt(x**2 + y**2 + z **2)
    a0 = 1
    ps = (1./81.) * 1./(6.*np.pi)**0.5 * (1./a0)**(3/2) * (r/a0)**2 * np.exp(-r/(3*a0)) * (3 * np.cos(th)**2 - 1)
    return ps


print("Generating scalar field..")
data = np.abs(np.fromfunction(psi, (50,50,100)))


print("Generating isosurface..")
verts, faces = pg.isosurface(data, data.max()/4.)

md = gl.MeshData(vertexes=verts, faces=faces)

colors = np.ones((md.faceCount(), 4), dtype=np.float32)
colors[:,3] = 0.2
colors[:,2] = np.linspace(0, 1, colors.shape[0])
md.setFaceColors(colors)
m1 = gl.GLMeshItem(meshdata=md, smooth=False, shader='balloon')
m1.setGLOptions('additive')

#w.addItem(m1)
m1.translate(-25, -25, -20)

m2 = gl.GLMeshItem(meshdata=md, smooth=True, shader='balloon')
m2.setGLOptions('additive')

w.addItem(m2)
m2.translate(-25, -25, -50)
    
if __name__ == '__main__':
    pg.exec()
