message: only mark elements with an alpha above the picking threshold
diff: +// only mark elements with an alpha above the picking threshold
  +if (uAlpha >= uPickingAlphaThreshold) {
  float marker = vMarker * 255.0;
  if (marker > 0.1) {
  if (mod(marker, 2.0) > 0.1) {
  @@ -6,3 +8,4 @@ if (marker > 0.1) {
  gl_FragColor.rgb = mix(uSelectColor, gl_FragColor.rgb, 0.3);
  }
  }
  +}
  \ No newline at end of file
  