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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) Vispy Development Team. All Rights Reserved.
# Distributed under the (new) BSD License. See LICENSE.txt for more info.
"""
This example shows how to use the `ArrowVisual` for a quiver plot
"""
from __future__ import division
import sys
import itertools
import numpy as np
from vispy import app, gloo, visuals
from vispy.visuals.transforms import NullTransform
class Canvas(app.Canvas):
def __init__(self):
app.Canvas.__init__(self, title="Quiver plot", keys="interactive",
size=(830, 430))
self.arrow_length = 20
self.grid_coords = None
self.line_vertices = None
self.last_mouse = (0, 0)
self.generate_grid()
self.visual = visuals.ArrowVisual(
color='white',
connect='segments',
arrow_size=8
)
self.visual.events.update.connect(lambda evt: self.update())
self.visual.transform = NullTransform()
self.show()
def generate_grid(self):
num_cols = int(self.physical_size[0] / 50)
num_rows = int(self.physical_size[1] / 50)
coords = []
# Generate grid
for i, j in itertools.product(range(num_rows), range(num_cols)):
x = 25 + (50 * j)
y = 25 + (50 * i)
coords.append((x, y))
self.grid_coords = np.array(coords)
def on_resize(self, event):
self.generate_grid()
self.rotate_arrows(np.array(self.last_mouse))
vp = (0, 0, self.physical_size[0], self.physical_size[1])
self.context.set_viewport(*vp)
self.visual.transforms.configure(canvas=self, viewport=vp)
def rotate_arrows(self, point_towards):
direction_vectors = (self.grid_coords - point_towards).astype(
np.float32)
norms = np.sqrt(np.sum(direction_vectors**2, axis=-1))
direction_vectors[:, 0] /= norms
direction_vectors[:, 1] /= norms
vertices = np.repeat(self.grid_coords, 2, axis=0)
vertices[::2] = vertices[::2] + ((0.5 * self.arrow_length) *
direction_vectors)
vertices[1::2] = vertices[1::2] - ((0.5 * self.arrow_length) *
direction_vectors)
self.visual.set_data(
pos=vertices,
arrows=vertices.reshape((len(vertices)//2, 4)),
)
def on_mouse_move(self, event):
self.last_mouse = event.pos
self.rotate_arrows(np.array(event.pos))
def on_draw(self, event):
gloo.clear('black')
self.visual.draw()
if __name__ == '__main__':
win = Canvas()
if sys.flags.interactive != 1:
app.run()
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