Creating A Polytunnel Skin

SketchUp
#1

I’m creating a model of a polytunnel greenhouse, which is essentially a steel tubular frame with a polythene skin stretched over it:

polytunnel

I’m having problems creating the polythene skin. As you can see, the skin is stretched between the hoops, but it doesn’t run straight across. Instead it curves in slightly from the outside of one hoop, stretches across to the next hoop, then curves out to the outside of that hoop.

I tried to create this effect using Soap Skin. I can’t use the actual 3D hoops I created because I wouldn’t get a closed loop. So, I created the basic shape using just edges instead. As you can see, I just used a couple of hoops and a basic semi-circle shape to practice on:

hoops

Because the shape is a single line thickness and the hoops have a diameter, I offset the shape so it was slightly outside the actual hoops. I then intended to tweak the Stress Ratio setting to get the effect I was after.

offset

However, when I ran Soap Skin nothing happened. After some trial and error, I realised that Soap Skin wouldn’t work on the straight sides of the hoops, but it worked fine when I removed them.

Am I doing something wrong, or is there a way around this? And Is using Soap Skin the best way to achieve what I want?

Cheers

Mark

Polytunnel.skp (1.1 MB)

#2

If you assume the curvature of the plastic is constant, can you not draw a section through it, create a face, and use Follow Me on the line of a hoop, and finally apply a suitable texture?

#3

Divide the line from the base then weld it.

ci-03
ci-03.gif1000×600 1.06 MB

3 Likes
#4

You might find Clothworks useful.
Cloth

By the way, can you edit your profile to tell us what you are actually using. I was just about to delete my post as your profile says free(web) and plugins don’t work with that. But then I remembered you had tried soaps skin, so you must be using something else.

6 Likes
#5

Thanks for all the input, I really appreciate it.

I’ve been playing around with the different suggestions over the last few days, and I’ve decided to go with Simon’s suggestion.

Cheers

Mark

#6

ClothWorks is a wonderful plugin