Problem unpacking texture buffer?

I’m trying to figure out why my shader won’t work; it’s a modified version of the example shader with the GLTF documentation repo.

If i change line 180 to float radius = position.w the output of the shader completely changes (completely black, as if position.w is NaN), but if i comment out line 178 the output of the shader does not change; in either case the light is white.

And i can’t figure out why this would be happening.

On ubuntu with an AMD implementation of openGL

changing it to float radius = max(1, position.w); fixed it… why? don’t know.