I had a problem when I clicked the mouse to get the sunflower ID. No matter where I click, the console prints the sunflower ID for the first click. Click on the F12 to open the console.
Online example: https://jsfiddle.net/x3br6f28/3/
You can create an instance of THREE.Frustum and then use THREE.Frustum.intersectsSprite() to perform the intersection test. The frustum is computed per frame like so: