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# Rotating Quad

Use a Timer to animate a quad

    from vispy import gloo, app
    from vispy.gloo import Program

    vertex = """
        uniform float theta;
        attribute vec4 color;
        attribute vec2 position;
        varying vec4 v_color;
        void main()
        {
            float ct = cos(theta);
            float st = sin(theta);
            float x = 0.75* (position.x*ct - position.y*st);
            float y = 0.75* (position.x*st + position.y*ct);
            gl_Position = vec4(x, y, 0.0, 1.0);
            v_color = color;
        } """

    fragment = """
        varying vec4 v_color;
        void main()
        {
            gl_FragColor = v_color;
        } """

    class Canvas(app.Canvas):
        def __init__(self):
            super().__init__(size=(512, 512), title='Rotating quad',
                             keys='interactive')
            # Build program & data
            self.program = Program(vertex, fragment, count=4)
            self.program['color'] = [(1, 0, 0, 1), (0, 1, 0, 1),
                                     (0, 0, 1, 1), (1, 1, 0, 1)]
            self.program['position'] = [(-1, -1), (-1, +1),
                                        (+1, -1), (+1, +1)]
            self.program['theta'] = 0.0

            gloo.set_viewport(0, 0, *self.physical_size)
            gloo.set_clear_color('white')

            self.timer = app.Timer('auto', self.on_timer)
            self.clock = 0
            self.timer.start()

            self.show()

        def on_draw(self, event):
            gloo.clear()
            self.program.draw('triangle_strip')

        def on_resize(self, event):
            gloo.set_viewport(0, 0, *event.physical_size)

        def on_timer(self, event):
            self.clock += 0.001 * 1000.0 / 60.
            self.program['theta'] = self.clock
            self.update()

    if __name__ == '__main__':
        c = Canvas()
        app.run()

Total running time of the script: (0 minutes 0.734 seconds)

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