I'm trying to model a bridge with a variable depth, like this:


I've created a curve for the alignment at the top of the bridge (on the roadway surface) and was hoping to use a second curve to deform the bottom of the bridge in the Z direction (only). I created a vertex group for the verts on the bottom of the bridge and added the second curve modifier; the problem is that instead of pulling the verts straight down to the bottom curve, the bottom of the bridge is deformed. Here's a more simplified example of what I'm trying to do:

enter image description here

I'm guessing that's done to maintain the length of the bottom of the object but that's not really what I want. I've tried modeling the bridge along one axis and deforming the bottom first (hence the bottom curve being on the X axis in the above picture). I've also tried placing a plane along the bottom curve and using a hook modifier to pull the verts down to the plane but that produced odd results. I've looked around on here but all of the other examples I've found that used two curves to deform an object had a similar result. It's a long bridge so I'd rather not have to apply the Array modifier and move each individual set of verts down to the bottom curve.

Can anyone help with this? It's really bugging me. Thanks in advance!!!

  • $\begingroup$ The brigde in your image is physically made of 2 pieces (actually 2 pieces joined by connecting pillars), is there any reason you need your model to be all one piece? $\endgroup$ Aug 14, 2020 at 1:14
  • $\begingroup$ Nevermind, I see what you mean. There are ways of straight modelling this though. Use the curve modifier to make the main curve of the bridge, as you have, and then in edit mode, hide the top vertices, and then pull select sections of the bottom ones down while using proportional editing to make the bottom have a varying height. $\endgroup$ Aug 14, 2020 at 1:30


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