glow.glsl

#define M_PI 3.1415926535897932384626433832795
#define M_TWO_PI (2.0 * M_PI)

float rand(vec2 n) {
	return fract(sin(dot(n, vec2(12.9898,12.1414))) * 83758.5453);
}

float noise(vec2 n) {
	const vec2 d = vec2(0.0, 1.0);
	vec2 b = floor(n);
	vec2 f = smoothstep(vec2(0.0), vec2(1.0), fract(n));
	return mix(mix(rand(b), rand(b + d.yx), f.x), mix(rand(b + d.xy), rand(b + d.yy), f.x), f.y);
}

vec3 ramp(float t) {
	return t <= .5 ? vec3( 1. - t * 1.4, .2, 1.05 ) / t : vec3( .3 * (1. - t) * 2., .2, 1.05 ) / t;
}
vec2 polarMap(vec2 uv, float shift, float inner) {
	float px = 1.0 - fract(atan(uv.y, uv.x) / 6.28 + 0.25) + shift;
	float py = (sqrt(uv.x * uv.x + uv.y * uv.y) * (1.0 + inner * 2.0) - inner) * 2.0;

	return vec2(px, py);
}
float fire(vec2 n) {
	return noise(n) + noise(n * 2.1) * .6 + noise(n * 5.4) * .42;
}

float shade(vec2 uv, float t) {
	uv.x += uv.y < .5 ? 23.0 + t * .035 : -11.0 + t * .03;
	uv.y = abs(uv.y - .5);
	uv.x *= 35.0;

	float q = fire(uv - t * .013) / 2.0;
	vec2 r = vec2(fire(uv + q / 2.0 + t - uv.x - uv.y), fire(uv + q - t));

	return pow((r.y + r.y) * max(.0, uv.y) + .1, 4.0);
}

vec3 color(float grad) {
	float m2 = iMouse.z < 0.0001 ? 0.15 : iMouse.y * 3.0 / iResolution.y;
	grad = sqrt(grad);
	vec3 color = vec3(1.0 / (pow(vec3(0.5, 0.0, .1) + 2.61, vec3(2.0))));
	vec3 color2 = color;
	color = ramp(grad);
	color /= (m2 + max(vec3(0), color));

	return color;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
	float m1 = iMouse.z < 0.0001 ? 1.6 : iMouse.x * 5.0 / iResolution.x;

	float t = iTime;
	vec2 uv = (fragCoord.xy - iResolution.xy * .5) / max(iResolution.x, iResolution.y);
	uv *= 1.5;
	float ff = 1.0 - uv.y;
	vec2 uv2 = uv;
	uv2.y = 1.0 - uv2.y;
	uv = polarMap(uv, 1.3, m1);
	uv2 = polarMap(uv2, 1.9, m1);

	vec3 c1 = color(shade(uv, t)) * ff;
	vec3 c2 = color(shade(uv2, t)) * (1.0 - ff);

	fragColor = vec4(c1 + c2, 1.0);
}