Note

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# Animate a 2D function

Illustrate how to plot a 2D function (an image) y=f(x,y) on the GPU.

    from vispy import app, gloo

    vertex = """
    attribute vec2 a_position;
    varying vec2 v_position;
    void main()
    {
        gl_Position = vec4(a_position, 0.0, 1.0);
        v_position = a_position;
    }
    """

    fragment = """
    #include "math/constants.glsl"
    //const float M_PI = 3.14159265358979323846;
    uniform float u_time;
    varying vec2 v_position;

    /**********************************************************
    Specify the parameters here.
    **********************************************************/
    const float z_offset = 1.;  // (z+z_offset)/z_max should be in [0,1]
    const float z_max = 2.;
    const float x_scale = 5.;  // x is between -x_scale and +x_scale
    const float y_scale = 5.; // y is between -y_scale and +y_scale
    const float t_scale = 5.; // scale for the time
    /*********************************************************/

    float f(float x, float y, float t) {

        // x is in [-x_scale, +x_scale]
        // y is in [-y_scale, +y_scale]
        // t is in [0, +oo)

        /**********************************************************
        Write your function below.
        **********************************************************/

        float k = .25*cos(t);
        return (cos(x)+k)*(sin(y)-k);

        /*********************************************************/

    }

    vec4 jet(float x) {
        vec3 a, b;
        float c;
        if (x < 0.34) {
            a = vec3(0, 0, 0.5);
            b = vec3(0, 0.8, 0.95);
            c = (x - 0.0) / (0.34 - 0.0);
        } else if (x < 0.64) {
            a = vec3(0, 0.8, 0.95);
            b = vec3(0.85, 1, 0.04);
            c = (x - 0.34) / (0.64 - 0.34);
        } else if (x < 0.89) {
            a = vec3(0.85, 1, 0.04);
            b = vec3(0.96, 0.7, 0);
            c = (x - 0.64) / (0.89 - 0.64);
        } else {
            a = vec3(0.96, 0.7, 0);
            b = vec3(0.5, 0, 0);
            c = (x - 0.89) / (1.0 - 0.89);
        }
        return vec4(mix(a, b, c), 1.0);
    }

    void main() {
        vec2 pos = v_position;
        float z = f(x_scale * pos.x, y_scale * pos.y, t_scale * u_time);
        gl_FragColor = jet((z + z_offset) / (z_max));
    }
    """

    class Canvas(app.Canvas):
        def __init__(self):
            app.Canvas.__init__(self, position=(300, 100),
                                size=(800, 800), keys='interactive')

            self.program = gloo.Program(vertex, fragment)
            self.program['a_position'] = [(-1., -1.), (-1., +1.),
                                          (+1., -1.), (+1., +1.)]

            self.program['u_time'] = 0.0
            self.timer = app.Timer('auto', connect=self.on_timer, start=True)

            self.show()

        def on_timer(self, event):
            self.program['u_time'] = event.elapsed
            self.update()

        def on_resize(self, event):
            width, height = event.physical_size
            gloo.set_viewport(0, 0, width, height)

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

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

Total running time of the script: ( 0 minutes 0.925 seconds)

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