//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;

const int octaves = 4;

//you can change these to uniforms
const float size = 40.0;
const float speed = 0.002;
const float strength = 0.01;

//pass in current_time
uniform float time;


float rand(vec2 coord){
    return fract(sin(dot(coord, vec2(56,78))*1000.0)*1000.0);
}

float noise(vec2 coord){
    vec2 i = floor(coord);
    vec2 f = fract(coord);

    float a = rand(i);
    float b = rand(i + vec2(1.0,0.0));
    float c = rand(i + vec2(0.0,1.0));
    float d = rand(i + vec2(1.0, 1.0));

    vec2 cubic = f * f * (3.0 - 2.0 * f);

    return mix( a, b, cubic.x) + (c - a) * cubic.y * (1.0 - cubic.x) + (d - b) * cubic.x *cubic.y;
}

float fbm(vec2 coord){
    float value = 0.0;
    float scale = 0.5;

    for(int i = 0; i < octaves; i++){
        value += noise(coord) * scale;
        coord *= 2.0;
        scale *= 0.5;
    }
    return value;
}

void main()
{
    vec2 coord = v_vTexcoord * size;

    vec2 noise;
    noise.x = fract(fbm(coord + time * speed)) * strength;
    noise.y = fract(fbm(coord + time * speed)) * strength;


    gl_FragColor = texture2D( gm_BaseTexture, v_vTexcoord + noise);

}