Sphere shader

number cx = 0.5;
number cy = 0.5;
number cz = 25;

number R = 0.2;

number x0=0.5;
number y0=0.5;
number z0=0;

extern number rot;

vec4 effect( vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords ){


  number y1=texture_coords.y;
  number x1=texture_coords.x;
  number z1=50;

  number dx = x1 - x0;
  number dy = y1 - y0;
  number dz = z1 - z0;

  number a = dx*dx + dy*dy + dz*dz;
  number b = 2*dx*(x0-cx) +  2*dy*(y0-cy) +  2*dz*(z0-cz);
  number c = cx*cx + cy*cy + cz*cz + x0*x0 + y0*y0 + z0*z0 + -2*(cx*x0 + cy*y0 + cz*z0) - R*R;

  number t = (-b-sqrt(pow(b,2)-4*a*c))/(2*a);

  if (t > 0) {




    number nx=(texture_coords.x-cx)/R/2;
    number ny=(texture_coords.y-cy)/R/2;

    number tu = asin(nx)/3.14 + 0.5 ;
    number tv = asin(ny)/3.14 + 0.5 ;

    vec2 texcoords = vec2(mod(tu+rot,1),tv);

    vec4 pixel = Texel(texture, texcoords );
    return pixel;

  }
}