# Cloudy skies

Make a CanvasItem, like a ColorRect or a Sprite, into an animated cloudy sky. The clouds will slowly move and change shape.

``````// cloudy skies shader

uniform float cloudscale = 1.1;
uniform float speed = 0.01;
uniform float clouddark = 0.5;
uniform float cloudlight = 0.3;
uniform float cloudcover = 0.2;
uniform float cloudalpha = 8.0;
uniform float skytint = 0.5;
uniform vec3 skycolour1 = vec3(0.2, 0.4, 0.6);
uniform vec3 skycolour2 = vec3(0.4, 0.7, 1.0);
uniform mat2 m = mat2(vec2(1.6,1.2),vec2(-1.2,1.6)); // changement

// functions

vec2 hash( vec2 p ) {
p = vec2(dot(p,vec2(127.1,311.7)), dot(p,vec2(269.5,183.3)));
return -1.0 + 2.0*fract(sin(p)*43758.5453123);
}

float noise( in vec2 p ) {
float K1 = 0.366025404; // (sqrt(3)-1)/2;
float K2 = 0.211324865; // (3-sqrt(3))/6;
vec2 i = floor(p + (p.x+p.y)*K1);
vec2 a = p - i + (i.x+i.y)*K2;
vec2 o = (a.x>a.y) ? vec2(1.0,0.0) : vec2(0.0,1.0); //vec2 of = 0.5 + 0.5*vec2(sign(a.x-a.y), sign(a.y-a.x));
vec2 b = a - o + K2;
vec2 c = a - 1.0 + 2.0*K2;
vec3 h = max(0.5-vec3(dot(a,a), dot(b,b), dot(c,c) ), 0.0 );
vec3 n = h*h*h*h*vec3( dot(a,hash(i+0.0)), dot(b,hash(i+o)), dot(c,hash(i+1.0)));
return dot(n, vec3(70.0));
}

float fbm(vec2 n) {
float total = 0.0, amplitude = 0.1;
for (int i = 0; i < 7; i++) {
total += noise(n) * amplitude;
n = m * n;
amplitude *= 0.4;
}
}

void fragment() {
vec2 res = 1.0 / SCREEN_PIXEL_SIZE;
vec2 p = FRAGCOORD.xy / res.xy; // changement
vec2 uv = p*vec2(res.x/res.y,1.0);    // changement
float time = TIME * speed ;
float q = fbm(uv * cloudscale * 0.5);

//ridged noise shape
float r = 0.0;
uv *= cloudscale;
uv += q - time;
float weight = 0.8;
for (int i=0; i<8; i++){
r += abs(weight*noise( uv ));
uv = m*uv + time;
weight *= 0.7;
}

//noise shape
float f = 0.0;
uv = p*vec2(res.x/res.y,1.0); // changement
uv *= cloudscale;
uv += q - time;
weight = 0.7;
for (int i=0; i<8; i++){
f += weight*noise( uv );
uv = m*uv + time;
weight *= 0.6;
}

f *= r + f;

//noise colour
float c = 0.0;
time = TIME * speed * 2.0;
uv = p*vec2(res.x/res.y,1.0); // changement
uv *= cloudscale*2.0;
uv += q - time;
weight = 0.4;
for (int i=0; i<7; i++){
c += weight*noise( uv );
uv = m*uv + time;
weight *= 0.6;
}

//noise ridge colour
float c1 = 0.0;
time = TIME * speed * 3.0;
uv = p*vec2(res.x/res.y,1.0);
uv *= cloudscale*3.0;
uv += q - time;
weight = 0.4;
for (int i=0; i<7; i++){
c1 += abs(weight*noise( uv ));
uv = m*uv + time;
weight *= 0.6;
}

c += c1;

vec3 skycolour = mix(skycolour2, skycolour1, p.y);
vec3 cloudcolour = vec3(1.1, 1.1, 0.9) * clamp((clouddark + cloudlight*c), 0.0, 1.0);

f = cloudcover + cloudalpha*f*r;

vec3 result = mix(skycolour, clamp(skytint * skycolour + cloudcolour, 0.0, 1.0), clamp(f + c, 0.0, 1.0));

COLOR.rgb = vec3(result);
}``````
###### Tags
environment, sky, weather

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