flakes.glsl

// based on shader by Nikos Papadopoulos, 4rknova / 2013 (https://www.shadertoy.com/view/llGSzw)
// Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

#define ENABLE_LIGHTING
#define ENABLE_SPECULAR

#define OFFSET_X 1
#define OFFSET_Y 1
#define DEPTH	 5.5

vec3 texsample(const int x, const int y, in vec2 fragCoord)
{
	vec2 uv = fragCoord.xy / iResolution.xy * iChannelResolution[0].xy;
	uv = (uv + vec2(x, y)) / iChannelResolution[0].xy;
	return texture(iChannel0, uv).xyz;
}

float luminance(vec3 c)
{
	return dot(c, vec3(.2126, .7152, .0722));
}

float hash1( uint n ) 
{
    // integer hash copied from Hugo Elias
	n = (n << 13U) ^ n;
    n = n * (n * n * 15731U + 789221U) + 1376312589U;
    return float( n & uvec3(0x7fffffffU))/float(0x7fffffff);
}

float rand (in vec2 point)
{
    uvec2 p = uvec2(point);
    return hash1( p.x + 1920U*p.y + (1920U*1080U) ); //*uint(iFrame)
}

vec3 normal(in vec2 fragCoord)
{
    float exponent = 100.0;
    float scale = 0.4;
    
	float u = rand(vec2(65.0, 87.0) + fragCoord * scale);
    float v = rand(fragCoord * scale);
    
	float phi = u * 2.0 * 3.141592;
    float cos_theta = pow(v, 1.0 / (exponent + 1.0));
    float sintheta = sqrt(1.0 - cos_theta*cos_theta);

	return vec3(cos(phi) * sintheta, sin(phi) * sintheta, cos_theta);
}

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
	vec3 n = normal(fragCoord);

#ifdef ENABLE_LIGHTING
	vec3 lp = vec3(iMouse.xy / iResolution.xy * iChannelResolution[0].xy, 200.);
	vec3 sp = vec3(fragCoord.xy / iResolution.xy * iChannelResolution[0].xy, 0.);
	
	vec3 c = vec3(0.9) * dot(n, normalize(lp - sp));

#ifdef ENABLE_SPECULAR
    float e = 64.;
    vec3 ep = vec3(iChannelResolution[0].x * .5, (iChannelResolution[0].y) * .5, 500.);
	c += pow(clamp(dot(normalize(reflect(lp - sp, n)), 
					   normalize(sp - ep)), 0., 1.), e);
#endif /* ENABLE_SPECULAR */
	
#else
	vec3 c = n * 0.5 + 0.5;
	
#endif /* ENABLE_LIGHTING */
	
	fragColor = vec4(c, 1);
}