Then with the foreground and background colours set as black and white ,choose...filter/render/clouds
Then choose filter/render/fibers with the following settings
which gives you this
this could be coloured like this to make long hair textures from scratch...but our goal here is for straight fold effect.
Next go to image/adjustments/gradient map and choose a colour combination you want....here ive went for yellow to blue so it highlights the effect better.
next go to filter.blur/motion blur and use the following settings.... -90 and full pixel distance.
which gives you this.
next go to filters/blur/gaussian blur and with a 3 pixel radius
gives you this.
This can be left like this for close folded material or stretched width ways for less folds.
Enjoy your folding