I wanted to post something on creating twists and curves in Blender, and invite you all to chime in with questions, or additional/alternate methods of accomplishing similar results.
Here is an item that can be thought of as a length of rope. It's dynamic, in that the shape of the curve can be modified easily with a single step:
First, the Twisty Part
1) Start with a cube and scale it on X and Y to about 0.3. You can do this by pressing S, then SHIFT+Z for an XY plane constraint.
2) Next scale it up on the Z axis to about 10.0.
You should now have a fairly long rectangle
3) Add some horizontal loops with the Loopcut tool. Press CTRL+R and scroll with the mouse wheel until you have about 25 cuts. Once in Loopcut mode, you can also just key in the value 25 and press enter.
Remember you can see the number of cuts in the info readout, located in lower left portion of the 3D header. You might also notice a message that reads “(S)mooth: off.” This is what we want, no smoothing of the cuts. Although it’s beyond the scope of this tutorial, you might want to press the S key to turn smoothing on and note the results when you confirm the loopcut.
4) Press CTRL+2 to add a Subsurf modifier at subdivision level 2, and activate the “Apply Modifier to Edit Cage” button in the Subsurf properties.
We need to duplicate all of the vertices to create 3 separate strands, and arrange them in a triangle of sorts.
5) Switch to Top view, press A to select all vertices and press SHIFT+D to duplicate and move the newly duplicated vertices to the side. Duplicate again, and position these toward the top, forming a triangle from 3 strands.
6) Position your 3D cursor at the top and center of the model and switch the pivot mode to 3D cursor. This is important in getting the twist to occur the way we want.
When you change the Pivot mode, you should see the Transform Manipulator move to the location of the cursor.
7) Switch to Side view and activate Proportional Edit with the O key. Change the falloff type to “Linear.” We want a direct falloff of twist from top to bottom.
8) Select only the top set of vertices. You should have 12 selected. Press R to rotate and Z to constrain around the Z axis. You’ll want to rotate about 1500 degrees.
You should notice the circle of influence of the Proportional Edit tool. If this circle is not big enough, you’ll see the twists stop abruptly somewhere along the length of the model.
9) Adjust the size of the Influence Circle with the mouse wheel until the twists extend down the length of the model.
10) Left click to confirm, and apply Set Smooth from the Editing buttons.
Your twisty rope should look something like the below image.
Next, the Curvy Part
1) From Front View, press SPACEBAR and Add->Curve->Bezier Curve. (Bezier is pronounced beh-zee-aye.) Make sure Proportional Edit is off. Remember you can toggle this with the O key.
2) While still in Edit mode, rotate the new curve 90 degrees so that it is vertical, and scale it up to about 10.0.
3) Position each end so that it is roughly aligned with the top and bottom of the rope model. (If it helps, switch to wireframe with the Z key so you can see this a little easier.) The curve should already be about the same size as the model, so this should be easy to do.
4) Tab out of Edit mode and select the rope model. From the Modifiers panel, add a Curve modifier. From the Curve modifier properties, enter the name of the Bezier Curve in the Object (Ob) box. The curve’s name should be “Curve.” Note that it is case sensitive.
5) Select the Y axis from the Curve modifier properties.
You’ll want to reposition the model so that it aligns again with the Curve object. Once you do, you’ll find that the model is deformed very effectively along the Bezier Curve object.
NOTE: The Origin Point of the Curve determines how well it aligns with the object. The origin of the model should match the origin of the curve for perfect alignment. If you create your Curve object at the very center of the model it deforms, it will most likely align perfectly on the first try, without having to drag the model around to align it with the Curve.
6) Select the Curve object and TAB into Edit mode.
You may have problems selecting the Curve object at this point, because it is inside of the rope model. You can a) switch to wireframe mode; b) ALT+RMB at the center of the rope model—this brings up a selection menu containing any object under the mouse cursor. Remember that in Edit mode, ALT+RMB is Edge Loop Select; but in Object mode, it brings up the Select Object menu. You may have to hunt with the mouse a little before you find the curve to select it.
7) Make sure both Curve vertices are selected by toggling with the A key, then press W for the Specials menu and choose Subdivide. This creates a new curve vertex between the two.
8) In the Editing context, from the “Curve and Surface” panel, turn on the 3D button, which is next to the “Back” and “Front” buttons. This will allow you to move the curve in full 3D space, instead of on the original 2 dimensions it was created on. If you ever have problems moving curve vertices, it could be that you don’t have 3D mode active.
You can now position your middle curve vertex to tweak the path of the rope, as well as adjust the Bezier handles for different angles and curve radii.
Please feel free to improve upon this and post your methods and results. You might want to experiment with things like modifier stack order, number of loopcuts, using a cylinder instead of a cube, etc.