Can you use Renderable Splines within the rtre Viewport?
In order for Renderable Splines to show up within the rtre Viewport, you must add an Edit Mesh modifier on top of the spline. This “converts” the geometry into a mesh that rtre can apply its lighting to and display. If you add an Edit Spline modifier before the Edit Mesh, you can even modify the spline while seeing the results update within the rtre Viewport.