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void mandelcup(inout vec3 p) {
        // c1 and c2 are adjustable constants, with default values c1=0. c2=2.
	vec2 z = complexDivision(p.xy,vec2(p.z,c1));	
	z = complexMult(z,z)*c2;
	p=vec3(2.*z.x, 2.*z.y, dot(z,z)-1.)/(dot(z,z)+1.);		
}

void mandelcup(inout vec3 p) {
        // c1 and c2 are adjustable constants, with default values c1=0. c2=2.
	vec2 z = complexDivision(p.xy,vec2(p.z,c1));	
	z = complexMult(z,z)*c2;
	p=vec3(2.*z.x, 2.*z.y, dot(z,z)-1.)/(dot(z,z)+1.);		
}

void mandelcup(inout vec3 p) {
        // c1 and c2 are adjustable constants, with default values c1=0. c2=2.
	vec2 z = (p.xy / p.z);	
	z = complexMult(z,z)*c2;
        float mag1 = dot(z,z)-1.; float mag2 = mag1+2.;
        z.xy = complexDivision(z.xy,vec2(mag2,c1));	
	p=vec3(2.*z.x, 2.*z.y, mag1/mag2);		
}

//vec2 z = (p.xy / p.z);
vec2 z = (p.xy * p.z);

void mandelcup(inout vec3 p) {
        // c1 and c2 are adjustable constants, with default values c1=0. c2=2.

        // squaring z appears to increase conformality and adds intesting
        // variations on outside julias
        if (squareZ)
                p.z*=p.z;

        // c1 can be used to modify the overall shape in nice ways and
        //  turn surface to aestethically pleasing quarternion-like smoothnes
        p.z+=c1;

        vec2 z;
        // inversion here produces another nice fractal with similar properties
        if (multiply)
                z = p.xy * p.z;
        else
                z = p.xy/p.z;

        z = complexMult(z,z)*c2;
        float mag1 = dot(z,z)-1.; float mag2 = mag1+2.;
        z.xy = complexDivision(z.xy,(vec2(mag2,0.)));
        p=vec3(2.*z.x, 2.*z.y, mag1/mag2);
}
 

void mandelcup(inout vec3 p) {
	
	vec2 z = p.xy/p.z; // or (p.z*p.z+1) for  more conformal
	z = complexMult(z,z)*c2;
	p=vec3(2.*z.x, 2.*z.y, dot(z,z)-1.)/(dot(z,z)+1.);	
}