CG artist Mike Campau creates what looks like beveled curves (below), but the cross sectional shape changes along the curve. Is there a trick to this or does he take the time and effort to manually manipulate a mesh to get these inspiring effects?
I think the easiest way is to use a Curve Modifier on an object. The object could be a deformed cylinder segment with an Array Modifier and a Displacement Modifier on it. I created using this technique the following image:
There where a couple things that I would like to mention here on this model. Firstly I used an 8 segement cylinder as base mesh and deformed it to make it a little more flat. Before the Displacement Modifier there is a Subdivision Modifier in the Modifier list. For the Displacment Modifier there is also one very important thing to mention: Texture Mapping. You couldn't use UV because it would repeat each segment so I used the Local Coordinates. The reason why this whole texture mapping thing is so imported is because the Clouds Texture I wanted to use has to be stretched along the curve. I achived that by scaling the object factor 10 on the (in my case X axis) and then in edit mode scale everything factor 0.1 so it looks the same as before but now the textures are stretched. This scaling sadly renders the array modifiers fit curve function unusable. For the Array Modifier which comes first in the Modifier list enable the Merge funciton. There is also one very important thing for the curve (maybe it's just for me) you have to set the U resolution higher else you will have steps.
My render doesn't looks like the work of Mike Campau but I am sure you can make something similar using this technique.
You can simplify this by manipulating a straight object by hand and use a curve modifier. It is much easier to change this not bended object using your favourite technique like sculpting, lattice, skin or completely by hand in edit mode.
Applying the curve modifier will deform the object along the curve. If the longitudinal resolution is not good enough, the deformed shape will not look continuous. Some tweaking or smoothing may be required.
I would like to add another option on how to achieve this, a more "clean" way to do this. Also I think this exactly how the artist did it.
Also make sure the 3d curve type is bezier to take advantage of the possibility to tilt vertices and add a "twist" effect.