Path: chuka.playstation.co.uk!news
From: rs108@mdx.ac.uk (Robert Swan)
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: dynamic tmd Q
Date: Sat, 06 Jun 1998 22:33:13 GMT
Organization: PlayStation Net Yaroze (SCEE)
Lines: 30
Message-ID: <3579c036.365181@www.netyaroze-europe.com>
References: <3579597C.25E5@livemedia.co.uk>
NNTP-Posting-Host: stu-dialup3.mdx.ac.uk
X-Newsreader: Forte Free Agent 1.11/32.235

>Is is possible to have a single TMD containing no textured polygons (ie
>only flat shaded etc), with both solid and transparent polys in it.
>Setting the attribute=(1 << 30) to turn transpareny on seems to make the
>whole TMD transparent.

yes it is possible. When you create the primitive you can set a bit in
the header part of that primitive that dictates whether or not it is
semi transparent. This is a default, and means that when the object is
drawn you dont have to set the attribute bit (1<<30) of the object to
get those primitives semi transparent. If you do set the attribute bit
to += (1<<30) then all of them are drawn semi. 

Whats interesting (but I havent tried it yet) is that you are
supposedly able to specify what format of semitransparency you use for
textured primitives (ie 100%+100%, 50%+50% etc). Unfortunately, we
seem to be stuck with 50%+50% for non textured primitives.

Anyway - to do this you need to set the ABE bit of the mode short part
when creating the primitive. (check out 1-15 of the Net Yaroze File
Format document, it will make it a bit clearer). For an example, check
out the unfinished racing game demo on my web site. Each section of
track has four primitives drawn semitransparently without using
(1<<30).

Robert Swan
rs108@mdx.ac.uk
http://www.netyaroze-europe.com/~middex2

ps - i will eventually sort out my tmd creation routines, document
them  but havent got the time at the moment.