Path: chuka.playstation.co.uk!news
From: Andreas Schrattenecker <andreas.schrattenecker@jk.uni-linz.ac.at>
Newsgroups: scea.yaroze.programming.3d_graphics
Subject: Re: Need help with TMD generation...
Date: Tue, 04 Nov 1997 17:12:35 +0100
Organization: PlayStation Net Yaroze (SCEE)
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David White wrote:

> I've got my program mostly up and running, but I have a few
> problems with polygon display. I'm not using the PC
> DXF-RSV-TMD conversion tools. Instead, I wrote a conversion
> program to write my models in Multigen (a 3D modeller)
> format. After cleaning up my models, I made a second
> conversion program to write TMD files directly.
>
> My models display, but with a these problems...
>
> NOTE: all polygons are gouraud triangles and quads
>
> 1. A few polygons are missing, while some others
>    appear and disappear as the camera location changes.
>    This is not a zsort problem as there are no polygons
>    closely behind these polygons; they are simply
>    disappearing.
>
> 2. Over half of my textured polygons blink with bizaar
>    colors and patterns even when the camera location
>    remains constant. I've verified that their uv
>    coordinates are unique. Other textured polygons in this
>    segment appear correct.
>
> 3. I can get Gouraud(gradation), No-Texture triangles,
>    but Gouraud(gradation), No-Texture Quads consistantly
>    generate errors (GPU Code 0h not supported) when I call
>    GsLinkObject4. I also get this problem with code that
>    generates a simple array of quads. Could the value
>    of 'olen' for gradation quads be wrong; I'm using '8'?
>
> 4. Close polygons sort randomly. I know that this is
>    due to the resolution on the Z-sort and I'll change
>    my model to accomodate the Z-sort resolution.
>
> Has anyone come across problems 1-3? I've run out of ideas
> to try and I'd appreciate any suggections. Thanks!
>
> David White

  1. I had the same problem with disappearing polygons (quads).
    I belief the reason for this is that quads are drawn as two
    triangles, but the calculations if the triangles are viewed from
front
    or back are not done separatly for both.Something like the average
    is backfaced -> both are not drawn, although one triangle is
    frontfaced. Try to use only triangles.
    If i am wrong, please let me know, because i want to use quads ->
    faster than 2 triangles, less memory.
3. Gouraud no-texture quads with mode=0x34, mode2=0x38 didnt work
    for me. Did work with mode=0x38,mode2=0x38. Maybe 0x24,0x38 for
    Gouraud,no-texture(gradated) is also wrong.


Andreas Schrattenecker