How to render a curve without creating meshes? I am able to render a curve by bevelling it.

However, for a scientific visualisation that I am working on, this doesn't render the way I wish it to. I would like the curve to render as a fixed width line irrespective of the distance from the camera.

Currently, I have to adjust the bevelling amount based on camera distance, and also play with rendering samples to get a smooth looking line.

Is there a cleaner approach that I am missing?

I am currently using the "cycles" renderer, but I am open to suggestions for any other renderer. Thanks!

Clarification: This is an animated visualisation. Hence, the distance from camera varies continuously. Here's an example video of what I am trying to do. The comet orbit is the curve I am worried about.
You could use OpenGL render (the button in the 3D View header) in Wireframe view mode. Every curve is rendered as a line without the need for any beveling. Animations can also be OpenGL rendered.

It is very fast. But there is no possibility to set the line width. It's always 1px.

To support transparency you have to set the shading mode to GLSL (press N in 3D View and look for Shading).