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dash-bezier.py
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dash-bezier.py
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"""Bezier quadratic example: Dash board
(c) Florian Wellmann, CG3
Run locally:
python bezier_dash_app.py
Deply e.g. over render.com
"""
import dash
from dash import dcc, html, Input, Output
from dash import callback_context
import plotly.graph_objs as go
import numpy as np
def quadratic_bezier(t, P0, P1, P2):
x0, y0 = P0
x1, y1 = P1
x2, y2 = P2
Bx = (1-t)**2 * x0 + 2*(1-t) * t * x1 + t**2 * x2
By = (1-t)**2 * y0 + 2*(1-t) * t * y1 + t**2 * y2
return (Bx, By)
app = dash.Dash(__name__) # , external_stylesheets=['https://codepen.io/chriddyp/pen/bWLwgP.css'])
server = app.server
app.layout = html.Div([
dcc.Graph(id='bezier-curve'),
html.Div([
html.Div([
html.H5("Point P0", style={'textAlign': 'center'}),
html.Div([
html.Label('x0', style={'paddingTop': '10px'}),
dcc.Slider(
id='x0-slider',
min=-5,
max=5,
value=0,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
html.Label('y0', style={'paddingTop': '10px'}),
dcc.Slider(
id='y0-slider',
min=-5,
max=5,
value=0,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
], style={'padding': '10px'}),
], className='three columns'),
html.Div([
html.H5("Point P1", style={'textAlign': 'center'}),
html.Div([
html.Label('x1', style={'paddingTop': '10px'}),
dcc.Slider(
id='x1-slider',
min=-5,
max=5,
value=1,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
html.Label('y1', style={'paddingTop': '10px'}),
dcc.Slider(
id='y1-slider',
min=-5,
max=5,
value=2,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
], style={'padding': '10px'}),
], className='three columns'),
html.Div([
html.H5("Point P2", style={'textAlign': 'center'}),
html.Div([
html.Label('x2', style={'paddingTop': '10px'}),
dcc.Slider(
id='x2-slider',
min=-5,
max=5,
value=2,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
html.Label('y2', style={'paddingTop': '10px'}),
dcc.Slider(
id='y2-slider',
min=-5,
max=5,
value=0,
step=0.1,
marks={i: str(i) for i in range(-5, 6)},
tooltip={"placement": "bottom", "always_visible": False},
className='dcc_control'
),
], style={'padding': '10px'}),
], className='three columns'),
html.Div([
html.H5("Parameter t"),
dcc.Slider(id='t-slider', min=0, max=1, value=0, step=0.01, marks={i/10: str(i/10) for i in range(0, 11)},
tooltip={"placement": "bottom", "always_visible": False})
], className='three columns'),
], className='row', style={'marginTop': '20px', 'marginBottom': '50px'})
], style={'textAlign': 'center', 'width': '90%', 'maxWidth': '1100px', 'margin': '0 auto'})
@app.callback(
Output('bezier-curve', 'figure'),
[Input('t-slider', 'value'),
Input('x0-slider', 'value'),
Input('y0-slider', 'value'),
Input('x1-slider', 'value'),
Input('y1-slider', 'value'),
Input('x2-slider', 'value'),
Input('y2-slider', 'value')]
)
def update_graph(t, x0, y0, x1, y1, x2, y2):
ctx = callback_context
if not ctx.triggered:
trigger_id = 'No inputs yet...'
else:
trigger_id = ctx.triggered[0]['prop_id'].split('.')[0]
P0 = (x0, y0)
P1 = (x1, y1)
P2 = (x2, y2)
# Compute the Bézier curve
t_values = np.linspace(0, 1, 100)
curve_points = [quadratic_bezier(t_val, P0, P1, P2) for t_val in t_values]
curve_x, curve_y = zip(*curve_points)
# Point at current t value
point_t = quadratic_bezier(t, P0, P1, P2)
# Intermediate points for construction lines
point_t1 = ((1-t)*x0 + t*x1, (1-t)*y0 + t*y1)
point_t2 = ((1-t)*x1 + t*x2, (1-t)*y1 + t*y2)
# Create Plotly traces
trace_curve = go.Scatter(x=curve_x, y=curve_y, mode='lines', name='Bézier Curve')
trace_control_points = go.Scatter(x=[x0, x1, x2], y=[y0, y1, y2], mode='markers', name='Control Points', marker=dict(color='red'))
trace_point_t = go.Scatter(x=[point_t[0]], y=[point_t[1]], mode='markers', name=f'Point at t={t:.2f}', marker=dict(color='green', size=12))
trace_construction_lines = go.Scatter(x=[x0, x1, x1, x2, point_t1[0], point_t2[0]], y=[y0, y1, y1, y2, point_t1[1], point_t2[1]], mode='lines', name='Construction Lines', line=dict(dash='dash', color='magenta'))
# Combine traces into a figure
figure = {
'data': [trace_curve, trace_control_points, trace_point_t, trace_construction_lines],
'layout': go.Layout(
title='Quadratic Bézier Curve with t Parameter',
xaxis={'title': 'X', 'range': [-5, 5]},
yaxis={'title': 'Y', 'range': [-5, 5]},
margin={'l': 40, 'b': 40, 't': 40, 'r': 10},
legend={'x': 0, 'y': 1},
hovermode='closest'
)
}
return figure
if __name__ == '__main__':
app.run_server(debug=True)