 varying vec3 vertLightDir;
 
 #define PI radians(180.)
+#define TWO_PI radians(360.)
 
 // adapted from http://stackoverflow.com/a/26127012/128511
 // https://www.vertexshaderart.com/art/79HqSrQH4meL63aAo/revision/9c9YN5LwBQKLDa4Aa

  // try a different way of displacing - spiral?
  vec4 vertSpiral = vertex;
  float pointRads = vertexIndex * 0.01;
  float pointRadius = vertexIndex * 0.01;
  vertSpiral.x = cos(pointRads) * pointRadius;
  vertSpiral.y = sin(pointRads) * pointRadius;
  vertSpiral.z = vertSpiral.z; // + displaceStrength * textureColor.r;

  // or a sphere :-D
  vec4 vertSphere = vec4(fibonacciSphere(totalVerts, vertexIndex) * height * 0.5 * textureColor.r, vertex.a);

  // animate between layouts
  float easedMix = smoothstep(0.1, 0.9, mixVal);
  // vec4 mixedVert = mix(vertGrid, vertSpiral, easedMix);
  vec4 mixedVert = mix(vertPolar, vertGrid, easedMix);
  // vec4 mixedVert = mix(vertSphere, vertSpiral, easedMix);

  // custom point size - use color to grow point
  float finalPointSize = pointSize * (1. + (easedMix * (textureColor.r * 4.)));
