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Giving pages some shape :

[0, .1, .15, .17, .15, .1, .05, 0, -0.01, 0, 0].map( (c,j) => { for (let i=0;i<xDiv+1;i++){ sheet.geometry.attributes.position.setZ(j+i*(xDiv+1),c) } })
sheet.geometry.attributes.position.needsUpdate = true

Not the most compact (fading sin) but works.

(original)