juliasetfractal.txt

//#ifdef GL_ES
#define MAX_ITER 20


//z starts with an initial value of the pixel(c1) and then you 
//add c2 in the iteration which can 
//be a constant or mouse position

float fJulia(vec2 c1, vec2 c2){
    float l = 0.;
    vec2 z = c1;
    for(float i=0.;i<float(MAX_ITER);i++) {
        if (z.x*z.x + z.y*z.y > 4.) {
        	return l;
            break;	
        }
        float xtemp = z.x*z.x-(z.y*z.y);
        z.y = 2.*z.x*z.y + c2.y;
        z.x = xtemp + c2.x;
        l+=1.;
    }
    return l;
}

vec3 trueCmap(float n)	{  
    // GLSL has it's own syntax for creating arrays . . .
    if (n == float(MAX_ITER)){
    	vec3 black = vec3(0.,0.,0.); 
        return black;
    }
    vec3 cMap[6] = vec3[6](vec3(1.,0.,0.), vec3(1.,0.,1.), vec3(0.,0.,1.), vec3(0.,1.,0.), vec3(1.,1.,0.), vec3(1.,0.5,0.)) ;
    //vec3 cMap[3] = vec3[3](vec3(1.,0.,0.), vec3(1.,0.,1.), vec3(0.,0.,1.));//, vec3(0.,1.,0.), vec3(1.,1.,0.), vec3(1.,0.5,0.)) ;
    float quotient = float(cMap.length()) * n / float(MAX_ITER);
    float lowerIndex = floor(quotient);
    float upperIndex = ceil(quotient);
    highp int lIndex = int(lowerIndex);
    highp int uIndex = int(upperIndex);
    float fraction = quotient - lowerIndex;
    vec3 c = cMap[lIndex] + fraction * (cMap[uIndex] - cMap[lIndex]);
    
return c;
}


vec4 nmap(float n) {
	vec3 colmap;
    if (float(n) <= float(MAX_ITER)) {
        float quotient = float(n) / float(MAX_ITER);
        float color = clamp(quotient,0.,1.);
        	if (quotient > 0.5) {
        	// Close to the mandelbrot set the color changes from green to white 
 				colmap = vec3(0.); //(color,1.,color);
        	}
        	else {
                colmap = vec3(0.,color,0.);
            }
    }
    return vec4(colmap,1.);
}


void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = fragCoord.xy/iResolution.xy;
    float aspect = iResolution.y/iResolution.x;
    vec2 p = uv*2.-1.;
    p.y*=aspect;
    float n = fJulia(p*2.);
    fragColor = vec4(trueCmap(n),1.);
}