Path: chuka.playstation.co.uk!scea!peter_alau@playstation.sony.com From: Tim O'Neil Newsgroups: scea.yaroze.programming.3d_graphics Subject: Re: Polygon subdivision Date: Sat, 25 Apr 1998 02:44:48 -0400 Organization: @Home Network Member Lines: 34 Message-ID: <35418660.1F32CB73@home.com> References: NNTP-Posting-Host: cr785161-a.rchrd1.on.wave.home.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.02 [en]C-AtHome0402 (Win95; U) wayne a. lee wrote: > > I've been playing with object subdivision (the attribute field of GsDOBJ2). > In my project, for my models, it turns out that using a subdivision of > GsDIV2 (4x4) is a good balance between texture distortion and speed. Then I > thought that things might go faster if I pre-subdivided the models myself, > in the modeller, and not use any runtime object subdivision, thinking I > would save on the calculation time. > > However, when I tried this, my demo ran *slower*, up to 60% slower, > depending! I confirmed that the same number of polygons were being drawn to > the screen in both cases. > > I'm wondering if this is cache-related? My models (unsubdivided) are *very* > simple, basically one to 16 quads with different textures. The > presubdivided ones are much bigger (16x more polygons). > > -- > wayne a. lee > How exactly are you submitting these faces to be drawn? If you are using more than a static number of function calls it will definately slow down. Consider that for every call on the playstation to any function involves loading all the parameters onto the stack, saving up to 8 temporary registers, jumping, executing the required code and then restoring these temporaries. Mind you this does depend on how the compiler deals with the temporary registers, but it does involve the 3 arguments to GsSortOt at the least, so if you are increasing the number of funciton calls, then things will invariably slow down a fair bit. Then again, the subdivision routines in the PSX might be doing some internal optimizations with the transformations or sorting.