Path: chuka.playstation.co.uk!news From: "SCEE" Newsgroups: scee.yaroze.programming.3d_graphics Subject: Re: Help: GsSortObject4 & GsSortOT Date: Tue, 28 Oct 1997 17:56:03 -0000 Organization: PlayStation Net Yaroze (SCEE) Lines: 64 Message-ID: <6359id$ju011@chuka.playstation.co.uk> References: <344e12ea.11334163@news.playstation.co.uk> <344E2A0F.15B5@interactive.sony.com> <3450cb36.3408555@news.playstation.co.uk> <632bv2$ju04@chuka.playstation.co.uk> <34560277.2468861@news.playstation.co.uk> NNTP-Posting-Host: 194.203.13.10 X-Newsreader: Microsoft Outlook Express 4.71.1712.3 X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 I'm starting to get confused now, I hope I get all this right. >I'm more trying to establish exactly what GS is up to as I haven't >found anything that makes it clear. > >You can set the OT Length to between 1 and 14 (powers of 2). > >Does GS *automatically* shift your Z values such that the OT can take >a world using values of 0-65000? > >For an OT length 14, GS would always shift Z by 2. >For an OT length 13, GS would always shift Z by 3 >etc. >etc. What happens is Gs crams the 16-bit Z into a 14-bit OT, this is internal. > >This would mean that the OT_SHIFT used when adding objects to the OT >is there purely to allow worlds bigger than 65000 odd. > >I'm sure in some early demo code wwhen an OT of length 12 was used an >OT shift of 2 was added. I did a quick test and I trashed my code when >not shifting my object's Z value by the expected amount, but it wasn't >exactly a 100% solid test. When you perform the shift it moves the Z value right to knock off the extra bits, so that the primatives fit into the required OT size. This is why when using the usual settings, it looks as if OT 14 shifts 2, OT 13 shifts 3 (the shift 2 is done by Gs any additional shift is done by you). I hope I haven't misled you with my previous mails on these points. > >Also, again I have read some conflicting information about something >else: > >I would have thought a smaller OT reduces memory useage as well as >increases rendering speed and leaves primitive creation speed >unchanged. It doesn't save that much memory the majority is taken up by the GPU work area. > >I'm sure in the docs it hinted that a smaller OT actually works >slower. The only reason I can think of why a smaller OT would be slower is that there are bigger linked lists to get through. A larger OT may result in more empty regions, which slows everything down, so normally you should use the smallest possible OT to achieve the desired result. > >Again, wouldn't be hard to test but if you guys already know ?-) > >Finally, saw that CD on one of the playstation mags. What is on there >exactly? Which CD? Where getting some Yaorze stuff on Official PlayStation Magazine in the coming months. Stuart