Polyline Fixes

[bagnell]

This has two fixes for #695.

• Culls polylines with width less than 1.0.
• Set polyline bounding sphere center x coordinate to 0.0 to prevent culling by the near plane.

[mramato]

While I'm fine with this. From a pure technical standpoint, should this be <= 0.0 instead of < 1.0? Is a width between 0 and 1 never valid use case? @pjcozzi ?

[pjcozzi]

I would suggest not doing this check here at all. A more efficient and convenient solution is to write the show component in the vertex data as (show && width > 0.0). For example, see writeOriginAndShow in BillboardCollection.js.

As for widths less than 1.0, I would have to try it.

[mramato]

Other than that one question, this all looks good to me. Original problem is gone, tests pass.

[bagnell]

@pjcozzi @mramato This is ready. I made it so that the width must be greater than zero instead of at least one. Let me know if that's OK.

[pjcozzi]

Code is OK with me. @mramato merge when you're ready. Also, we might want a test for width === 0 just like we have a test (I assume) for show === false.

[mramato]

Since Cozzi mentioned it, a test would be good. Assuming we have one for show, it should just be a copy/paste job.

[bagnell]

@mramato I added a test. This is ready.