Path: chuka.playstation.co.uk!news
From: "D Smethurst" <dave@ulthwe.demon.co.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: 3D Uneven Terrain
Date: Sun, 26 Jul 1998 10:53:57 +0100
Organization: PlayStation Net Yaroze (SCEE)
Lines: 91
Message-ID: <6pg28c$3ue1@chuka.playstation.co.uk>
References: <6otsjq$cv91@scea> <35B328FC.E0B64296@hinge.mistral.co.uk>
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Craig Graham wrote in message <35B328FC.E0B64296@hinge.mistral.co.uk>...
>Nathan Miller wrote:
>
>> 1) You make a data structure in addition to the tmd that represents the
>> terrain that divides the level into your average cell based world:
>>  struct mapdata
>> {
>>  int flag;
>>  //Link list containing items and such for cell
>> };
>>  mapdata level1[50][50];
>
>That's similar to a Voxel.
>
>What you can do is generate a 'height map' bitmap on the fly:
>Here's one way :
>1) Setup the fogging so that you get a fairly good fade out effect from
high
>intensity
>pixels at the highest point on the map to low intensity/black at the lowest
>point of
>the map.
>2) Have the playstation render a top-down view of your map model to an
offscreen
>
>area of VRAM (size is relative to how accurate you need the map to be).
>3) Copy the VRAM area into DRAM - viola, you've generated the height map.
>Black == low , white==high.


Interesting way to generate a landscape, I've seen it used alot before
though
I haven't coded one this way yet. I suppose it would make map creation
easier aswell.

Anyway , I've done a similar project under DOS/professional PSX Dev kit.
I used an array of int's to give a landscape height at a certain point on
the map.
The co-ords for the polygons were then generated from this with a tile size
of 32x32 so that the x & z components were generated so that each tile
was aligned with the one next to it. The height (y) component was generated
for each of the 4 tile points by taking the 3 neighboring values and finding
the heighest point.
i.e.

3 4 4
3 2 2
2 1 1

Given this general array above when you generate the 4 corner y values
you get
4  4
3  2

Then these are also applied a height factor (I think I used 16 !) to give
it's relative
display position.

The map only needed to be generated once as all other functions of
moving/rotating/
scaling can be done after, it also means that I can write (in the end) a
program to
generate each map cell from the map and save it to a file.
Of course I haven't done much on this recently due to time constraints etc
though
I am working on a 3Dfx (Glide) version atm ... and a D3D version some time
in the future when I get to it.

>Advantages:
>1) This solves the problem of interpolating polygons yourself to generate
the
>height map.
>2) You only have to do it once for the current map.
>3) If you want high accuracy and a real big map, you can regenerate the
height
>map
>every N frames or whenever the player moves to far.
>4) Can be used with dynamically generated TMD landscapes.
>5) Very Very fast.
>
>> 2) you check the players height level directly with the tmd's vertex data
>
>Can be done, but you then have to interpolate to create the polygon
planesto get
>the height at a given point.


D.