Simple Sky with Noise Clouds

I’ve been playing around with the new sky shaders lately and have come up with this

 

Shader contains:

  • rayleigh and mie scattering
  • parameters to change the sky color
  • basic noise clouds
  • basic sun

 

It’s not the prettiest, but I thought I’d still share

Shader code
shader_type sky;
render_mode use_half_res_pass, use_debanding;

uniform vec4 baseColor : source_color = vec4(0.0, 0.64, 0.84, 1.0);
uniform vec4 horizonColor : source_color = vec4(0.36, 0.59, 0.86, 1.0);

uniform float horizonHeight : hint_range(-1.0, 1.0, 0.01) = -0.2;
uniform float rayleighCoefficient : hint_range(0.0, 1.0, 0.01) = 0.2;
uniform float mieCoefficient : hint_range(0.0, 1.0, 0.01);
uniform float mieEccentricity : hint_range(-1.0, 1.0, 0.01) = 0.8; 

uniform float sunDiskScale: hint_range(0.0, 1.0, 0.01) = 0.2;
uniform float sunSmoothing : hint_range(0.0, 1.0, 0.1) = 0.5;

uniform sampler2D cloudTexture;
uniform sampler2D cloudCoverageTexture;

// Calculate the total amount of light scattered by Rayleigh scattering for all lights
vec3 rayleighScattering(float cos_theta) {
	float rayleighSunPhase = 0.75 * (1.0 + cos_theta * cos_theta);
	vec3 rayleighColor = horizonColor.rgb * rayleighCoefficient * rayleighSunPhase;
	
	return rayleighColor;
}

// Calculate the total amount of light scattered by Mie scattering for all lights
vec3 mieScattering(float cos_theta, float g) {
	float mieSunPhase = ((1.0 - g * g) / (4.0 * PI)) * (1.0 + g * g - 2.0 * g * cos_theta) / pow(1.0 + g * g - 2.0 * g * cos_theta, 1.5);
	vec3 mieColor = horizonColor.rgb * mieCoefficient * mieSunPhase;
	
	return mieColor;
}

void sky() {
	// compute stereographic coordinates
	float theta = acos(dot(EYEDIR, vec3(0, 1, 0)));
	float phi = atan(EYEDIR.z, EYEDIR.x);
	float r = 2.0 * tan(theta / 2.0);
	vec2 stereographic = r * vec2(cos(phi), sin(phi));
	vec2 texCoords = vec2(0.5, 0.5) + stereographic * vec2(0.5, -0.5);
	
	float cos_theta = dot(EYEDIR, LIGHT0_DIRECTION);
	
	// Solar disk
	float sunDir = distance(EYEDIR, LIGHT0_DIRECTION);
	float sunPos = 1.0 - clamp(sunDir / sunDiskScale, 0.0, 1.0);
	float sunAngularDiameterCos = cos(sunPos * sunDiskScale);
	float sunAngularDiameterCos2 = cos(sunPos * sunDiskScale * sunSmoothing);
	float sunDisk = smoothstep(sunAngularDiameterCos, sunAngularDiameterCos2, cos_theta);
	vec4 sun = vec4(LIGHT0_COLOR * LIGHT0_ENERGY, sunDisk);
	
	vec3 totalScattering = mieScattering(cos_theta, mieEccentricity) + rayleighScattering(cos_theta);
	
	vec4 clouds = mix(texture(cloudTexture, texCoords), vec4(0), texture(cloudCoverageTexture, texCoords));
	float colorGradient = EYEDIR.y - horizonHeight;
	vec3 skyColor;
	skyColor = mix(horizonColor.rgb, baseColor.rgb, colorGradient);
	skyColor = mix(skyColor.rgb, sun.rgb, sun.a);
	skyColor = mix(skyColor.rgb, clouds.xyz, clouds.rgb);
	
	COLOR = skyColor + totalScattering;
}
Tags
atmosphere, clouds, sky, Sun
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

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