The Archicad 24 pillow that Barry highlighted is 3000 polygons so if you were to use this on your seat it would total 18000 polygons plus the frame which would be around 200 polygons depending on the level of detail. The total polygon count would make it very unfriendly.
So if you want it to be realistic the polygon count will be high.
I will put some thought into a parametric cushion that you can control the resolution for, but I fear the issue of realism over polygon count will still exist in such an element.
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Push the envelope & watch it bend
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