// -----------------------
//  Demo for transparence
// -----------------------

//  image size

width  = 300;
height = 300;

//  fix rotation

rot_x=0.2;
rot_y=-0.33;
rot_z=-3.33;

//  fix scaling

double sf = 0.25;
 
scale_x=sf;
scale_y=sf;
scale_z=sf;

//  fix position and perspective

spec_z = 25.0;
perspective=central;
radius=9.0;

//  fix surface properties

transparence=60;
transmitted =70;
thickness   =14;

surface_red  =255;
surface_green=100;
surface_blue =130;
inside_red   =255;
inside_green =100;
inside_blue  =130;

//  fix light

illumination=ambient_light+
             diffuse_light+
             reflected_light+
             transmitted_light;
ambient=20;
smoothness=30;
 
light1_x=1-00;
light1_y=100;
light1_z=100;
light1_vol=80;
 
light3_x=100;
light3_y=20;
light3_z=50;
light3_vol=60;
 
light8_x=-100;
light8_y=100;
light8_z=-100;
light8_vol=0;

//  define the sextic
 
double t=(1+sqrt(5))/2;
 
poly f1=t^2*x^2-y^2;
poly f2=t^2*y^2-z^2;
poly f3=t^2*z^2-x^2;
 
poly g =(x^2+y^2+z^2-1)^2;
 
surface=-(4*f1*f2*f3-(1+2*t)*g);

epsilon=0.0001;
iterations=30;

//  draw it

clear_screen;
draw_surface;