glsl-atmosphere

Renders sky colors with Rayleigh and Mie scattering.

Install

npm install glsl-atmosphere

Example

Javascript

var quad = Geometry(gl)
    .attr('aPosition', [
        -1, -1, -1,
         1, -1, -1,
         1,  1, -1,
        -1, -1, -1,
         1,  1, -1,
        -1,  1, -1
    ]);

program.bind();
quad.bind(program);
program.uniforms.uSunPos = [0, 0.1, -1];
quad.draw();

Vertex Shader

attribute vec3 aPosition;

varying vec3 vPosition;

void main() {
    gl_Position = vec4(aPosition, 1.0);
    vPosition = aPosition;
}

Fragment Shader

varying vec3 vPosition;

uniform vec3 uSunPos;

#pragma glslify: atmosphere = require(glsl-atmosphere)

void main() {
    vec3 color = atmosphere(
        normalize(vPosition),           // normalized ray direction
        vec3(0,6372e3,0),               // ray origin
        uSunPos,                        // position of the sun
        22.0,                           // intensity of the sun
        6371e3,                         // radius of the planet in meters
        6471e3,                         // radius of the atmosphere in meters
        vec3(5.5e-6, 13.0e-6, 22.4e-6), // Rayleigh scattering coefficient
        21e-6,                          // Mie scattering coefficient
        8e3,                            // Rayleigh scale height
        1.2e3,                          // Mie scale height
        0.758                           // Mie preferred scattering direction
    );

    // Apply exposure.
    color = 1.0 - exp(-1.0 * color);

    gl_FragColor = vec4(color, 1);
}

API

#pragma glslify: atmosphere = require(glsl-atmosphere)

`vec3 atmosphere(vec3 r, vec3 r0, vec3 pSun, float iSun, float rPlanet, float rAtmos, vec3 kRlh, float kMie, float shRlh, float shMie, float g)`

Returns a vec3 representing the color of the sky along a view direction.

Takes:

vec3 r normalized ray direction, typically a ray cast from the observers eye through a pixel
vec3 r0 ray origin in meters, typically the position of the viewer's eye
vec3 pSun the position of the sun
float iSun intensity of the sun
float rPlanet radius of the planet in meters
float rAtoms radius of the atmosphere in meters
vec3 kRlh Rayleigh scattering coefficient
vec3 kMie Mie scattering coefficient
float shRlh Rayleigh scale height in meters
float shMie Mie scale height in meters
float g Mie preferred scattering direction

For an Earth-like atmosphere, see the settings in the example above.

wwwtyro/glsl-atmosphere

wwwtyro

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