I ported this into Qrack when MH posted the tut back on QSG.
If you want to see the end result you can try R_SKYSCROLL 1 in Qrack or MHQUAKE.
The new z-fail method speeds the rendering 10x so it is VERY useful on less powerful machines, like my silly DELL desktop at work that has an integrated Intel (brookdale) card.
EDIT:
Oops! I just re-read your message to conclude u meant PUT it. I thought for a minute meant check it OUT.
The bulk of the code goes in gl_warp.c
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random MH quote: Hot damn Jethro, this sho' is purdy!!!