   vec2 res = vec2(.0);
 
   float transitionTime = 10.;
-  float end0 = 11.;
+  float end0 = 20.;
   float end1 = 34.;
   float end2 = 50.;
   float end3 = 70.;

  // float plasma1 = calcPlasma(pos.x, pos.y, pos.z, a / 10.0);
  return vec2(
    // tunnel shape
    sdBloodVein(pos + vec3(2.0,1.5,0.0)),

    // blobby surface
    // + 0.05 * sin(10.0 * pos.x) * sin(10.0 * pos.y) * sin(10.0 * pos.z),

    // color
    170.0 / 3.0
  );
}




float sdBloodVein(vec3 p) {
  vec3 c = vec3(2.,3.,5.);
  return -(length(p.xy-c.xz)-c.y);
}

float sdBloodVein2(vec3 p) {
  return abs(length(vec2(length(p.xz)-3.,p.y)) - .3);
}


