vispy drifting sinusoid example

simple drifting sinusoid

# gpu drifting sinusoid.
# based on gpuimage example in docs:
# https://github.com/vispy/vispy/blob/master/examples/basics/gloo/gpuimage.py

from vispy import app, gloo

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

fragment = """
uniform float u_time;
varying vec2 v_position;
const float z_offset = 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) {
    float phase_shift = 2; 
    float spatial_freq = 3.0;
    return cos(x*spatial_freq - phase_shift*t); 
}

//greyscale color scheme (needs work)
vec4 greyscale(float x) {
    return vec4(x, x, x, 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 = greyscale((z + z_offset) / (z_max));
}
"""

#check out canvas.fps and other things
#%%
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['xy_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()