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# Draw a Line

Simple demonstration of SceneCanvas containing a single line entity as its entire scenegraph.

    Generating points...
    Done

    import sys
    import numpy as np

    from vispy import app, scene

    canvas = scene.SceneCanvas(size=(800, 600), keys='interactive')

    N = 1000
    pos = np.empty((N, 2), np.float32)
    pos[:, 0] = np.linspace(50., 750., N)
    #
    color = np.ones((N, 4), dtype=np.float32)
    color[:, 0] = np.linspace(0, 1, N)
    color[:, 1] = color[::-1, 0]

    lines = []

    print('Generating points...')
    for i in range(20):
        pos = pos.copy()
        pos[:, 1] = np.random.normal(scale=5, loc=(i+1)*30, size=N)
        line = scene.visuals.Line(pos=pos, color=color, parent=canvas.scene)
        lines.append(line)
        line.transform = scene.transforms.STTransform()
    print('Done')

    def update(event):
        for line in lines:
            scale = [np.sin(np.pi * event.elapsed)+2,
                     np.cos(np.pi * event.elapsed)+2]
            line.transform.scale = scale

    timer = app.Timer('auto', connect=update, start=True)

    if __name__ == '__main__':
        canvas.show()
        if sys.flags.interactive == 0:
            app.run()

Total running time of the script: (0 minutes 0.951 seconds)

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