 
 
 float sdBloodVein(vec3 p) {
-  vec3 c = vec3(2.,5.,5.);
-  return abs(length(p.xy-c.xz)-c.y);
-}
-
-float sdBloodVein2(vec3 p, vec3 t) {
-  return -pow(p.x*p.x + p.z*p.z, 2.) + t.x * (p.x*p.x + p.z*p.z) + t.y * p.y*p.y + t.z;
+  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);
 }
 
 

  // 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
  );
}


  vec2 res = vec2(.0);

  float transitionTime = 10.;
  float end0 = 20.;
  float end1 = 34.;
  float end2 = 50.;
  float end3 = 70.;
