water-refraction.glsl

#define R 1.1

float wave(in vec2 uv, in vec2 center, in float radius) {
    vec2 s = uv - center;
    float r = length(s);
    float h = sin(r * 50.0 + float(iFrame) / 10.0) * 0.1 * (radius - r);    
    if(r >= radius)
        return 0.0;
    else
        return h;
}

float computeH(in vec2 uv) {
    return wave(uv, vec2(0.0, 0.0), 0.9)
         + wave(uv, vec2(1.0, 0.0), 0.9)
         + wave(uv, vec2(0.5, 1.0), 0.9)
         + 0.5;
}

vec2 displacement(float h, vec2 delta) {
    vec2 beta = asin(sin(delta) / R);
    vec2 x = tan(delta - beta);
    return x*h;
}

float derivativeX(vec2 uv, float e) {
    float h = computeH(uv);
    float h1 = computeH(uv + vec2(e, 0.0));
    float dh = h1 - h;
    return dh / (e);
}

float derivativeY(vec2 uv, float e) {
    float h = computeH(uv - vec2(0.0, e));
    float h1 = computeH(uv + vec2(0.0, e));
    float dh = h1 - h;
    return dh / (2.0 * e);
}

vec2 derivative(vec2 uv, vec2 e) {
    return vec2(derivativeX(uv, e.x), derivativeY(uv, e.y));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
	vec2 uv = fragCoord.xy / iResolution.xy;
    float h = computeH(uv);
    vec2 der = derivative(uv, vec2(1.0) / iResolution.xy);
    vec2 delta = atan(der);
    //fragColor = vec4(h, delta, 1.0);
    //fragColor = vec4(vec3(h), 1.0);
    //fragColor = vec4(h, der.y / 30.0, 0.0, 1.0) / 0.5 + 0.5;
    //fragColor = vec4(der.x / 40.0, -der.x / 40.0, 0.0, 1.0);
    //fragColor = vec4(delta.x/2.0, -delta.x/2.0, 0.0, 1.0);
	fragColor = texture2D(iChannel0, uv + displacement(h, delta) / 50.0);
}