Drawing 3D curve with varying width

I am trying to draw a curve in 3D in which the width may vary. I am doing something similar to what described in the following tutorial: Drawing smooth lines with cocos2d ios inspired by Paper

Meaning, i create quads (and triangles) with the desired width instead of using OpenGL width. The problem is that the triangles are actually in 2D - they are drawn in a specific plane. The width will look different, of course, from different angles.

Am i tackling this problem in the correct way? Is there a good solution for my problem?

You may want to look at this