Line could not be shown

myTestOfLineDisappear.html (4.7 KB)

The attached file attempts to extract lines from spotLightHelper(which is not added to scene), but the lines could not be shown. I am new to threejs. It’s quite possible I missed something important. Could anybody point it out for me?

Thanks in advance.

Your shared HTML code was not functional and full of errors. When sharing code in a topic, the idea is to provide a complete and running live example or GitHub repo.

I’ve ported your code to a fiddle and removed all non-relevant parts so it’s easier to understand the relevant bits for solving your issue:

Thanks for your advice. I’ve found the error.