This tutorial is in response to prixat, in my WIP thread, where I'm modeling a Capitone-style, art-deco modern sofa.  This is how to achieve the creases and button holes in the cushion, while still maintaining (hopefully) 100% quadrilateral topology.

I'm using 3dsmax 2013 to model this object, but hopefully you will be able to translate the procedure to whatever modeling app you are using.  I know that Blender and Cinema4D have similar polygon modeling tools to 3dsmax, so people using those apps should be able to reproduce the same results easily.  It's not a difficult process, if you have the tools in your app to do some of the operations.

Ok, start by creating a box, with whatever dimensions you wish your sofa cushion to be.  The length and height don't need to be precise, unless you are modeling for an Archi/Viz scene where space matters.  However, the amount of edges does count to get the right results.  So, make your box with length segments: 6;  width segments: 12; and height segments: 2.  It should look similar to this image:

The next step is to select every OTHER vertex on your box, in a step-selected, diagonal pattern, exactly like this:

It's important you select the verts in that exact pattern on each side. Once you have them selected, connect the selected vertices with edges, (in 3dsmax, just press "Connect" in the vertex subobect mode in the modifier panel) and you should end with a triangulated mesh that looks exactly like this:

Now select your centroid vertices, and chamfer them to about 2 or 3 centimeters, so the topology looks like this:

After you chamfer the vertices, you end up with a rounded Ngon where each vertice used to be. Go to polygon or face mode, and select each one of those Ngons, then Bevel them INWARD about 2 centimeters. They should look like this:

Now, go to vertex mode, and select ONLY the inside vertices of all your new bevels, and WELD only the inner vertices of the bevels together, so that you only have ONE single vertex or point on the inner part of your bevel. In 3dsmax, you would just select the inner vertices of the new bevels, click WELD, and adjust the tolerance until there's just one vertex left. Your bevels should look like inverted icecream cones if all went well, just like in the image below:

Next, go to edge mode, and select ONLY the cross-hatching edgeloops on your topology, as illustrated in RED in the image below:

Now, with those crosshatched edges selected, the next step is up to you on how you wish to proceed. If you own 3dsmax, I recommend getting a modifier called "Quad Chamfer", and using that to chamfer those edges, and inset the results, in order to keep perfect quad topology.

However, in any other app, or if you don't care to use Quad Chamfer modifier, then just extrude those edges INWARD (AKA, "intrude", in some applications) as deep as you like (the deeper the extrusion, the more pronounced the cushion folds will appear once smoothed. It should end up looking something like this:

Once you have your extruded edges, it's up to you if you want to add any support loops to the edges for a tighter appearance, but at this point, you should be able to add a subdivision smoothing with about 2 iterations, and you should end up with this:

That's it! Easy, right? Now, further details would be to add buttons in each of the "holes", or a seperate trim on the intruded edges. This is where polygon count will skyrocket, but this isn't intended to be a model you will use if your polygon budget is conservative anyway.

Good luck, and hopefully this helps or gives you some ideas for your own techniques.

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