Colliding Implicits

I was playing around with the problem of what to do when spline skeletons collide and how color should be normalized. Lucky included some field functions in his Starlight Penetrating project, so I gave those a try. It seems the the function F(d;radius) = (1 - d/radius)^2 seems to produce reasonable output. It is clearly better behaved than a simple average of all the colors should multiple auroras collide in image space. I have included an image with three splines on it. The field function defines the weights, and the final color at each pixel is a weighted average according to the specification that Lucky set out in his paper (without the inclusion of ambient color).

I think it's possible to do better. In particular the endpoint boundaries on the spline are too strong, even with the mixing. At this point, I am beginning to think we might benefit from casting multiple jitterred rays at the splines, which might reduce aliasing as well as the sharp discontinuities between the aurora bands.