BouncingSun.frag

/*
    This is a fragment shader file, if you don't know anything about it
    you can run it here online -> http://editor.thebookofshaders.com/
    just copy and paste the code
*/

precision mediump float;

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

float diatance(vec2 p1, vec2 p2){   //distance function
    return
        (sqrt(
            (pow( (p2.y - p1.y) , 2.0) + pow( (p2.x - p1.x), 2.0))
        ));
}

void main() {
    vec2 centre = vec2(u_resolution.x/2.0,u_resolution.y/2.0);
    float R,G,B,A, dist, size1, size2, tmp;
    vec3 color;


    size1 = 100.0;
    size1 *= ((abs(sin(u_time / 3.0))) + 0.5);          //--comment this line to stop growth
                                                        //  animation
    centre.y *= (abs(sin(u_time*2.0)));                 //--comment to stop position animation
    size2 = (size1 * 4.0);
    size2 *= (abs( sin( u_time / 2.0 )) / 5.0 ) + 0.8;  //--animating warmth | comment to stop

    dist = distance(gl_FragCoord.xy, centre);           //--distance of each pixel from centre
    if( dist <= size1){         //--sun color
        tmp = dist/size1;
        R = 1.0;
        G = (1.0 - pow((dist/size1)*0.9,8.0));
        B = (1.0 - pow(tmp,0.5));
    }
    else if(dist <= size2){     //--set shine/warmth color
        tmp = dist/size2;
        R = (1.0 - clamp(pow(tmp,5.0),0.0,0.7));
        G = (1.0 - clamp(pow(tmp,3.0),0.0,0.2));
        B = (pow (tmp,1.0));
    }
    else{                       //--set sky color
        R = 0.3;
        B = 1.0;
        G = 0.8;
    }

    color = vec3(R,G,B);
    A = 1.0;
    gl_FragColor = vec4(color,A);
}