Thanks for the reply maxxxmodelz, but I guess that wasn't it. I disabled smooth polygons, visible in raytracing, even cast shadows, and it is still a rectangle. I figure it has something to do with raytracing because if I drop the render setting one tick below enabling raytracing the blade renders perfectly, even with all of those options left on.

You can see the difference in the attached image. The one on the left is with the first option to raytrace. The one next to it is without raytracing enabled in the firefly engine.