[Algorithms] Terrain Organization

[Pai-Hung C. <pa...@ac...>]

Hi,

I have a terrain of 5000~6000 triangles (I would like to make it
higher) in my upcoming 3D RPG game (my master thesis).  (I am
using an ELSA Erazor X^2 GeForce card with Direct3D IM.)  I am
always wondering what is the best terrain orgnization algorithm to
organize and render my terrain.  Meanwhile I am planning to split
the terrain up to several _hierarchical_ chunks (with bounding
boxes) and, for each frame, I test each chunk against the current
viewing frustum (VF) to _recursively_ determine if it has to be
submitted to the transformation and rendering pipeline.  If an
_upper-level_ chunk is rejected, there is no need to go down to
the _lower-level_ chunks inside it, which can quickly reject a
huge amount of geometry.  This technique sounds extremely crude,
but, with its relatively low geometry management overhead, I think
it is very efficient, despite its "obviousness."  (Please correct
me if I am wrong.)  I know there are lots of other more
sophisticated/advanced techniques such as BSP and ROAM, but I
doubt if they are really worth their extra huge geometry
management cost in real-time 3D applications.  Here are my
opinions about the BSP and ROAM:  (Please correct me if I am
wrong.)

(1) BSP:
I think a basic BSP can only tell you what is _in front of_ you.
But most of the time you don't really want to draw everything that
is in front of you, but only those that are inside the current VF,
which still requires the VF testing.  Also, since BSP is in
triangle level, there will potentially be more texture stage
changes when rendered.

(2) ROAM:
This is way too complicated for my poor brain...  Tjhe idea of LOD
is great but I really doubt if ROAM is really worth its extra
management cost since you have to re-construct everything in each
frame.  This leads me to the thinking of whether ROAM has other
better targeted applications than real-time 3D games running on
PCs.

Apart from the three techniques mentioned above, are there other
universally agreed better ways to handle richly-textured terrain
in 3D game?  Any comments are highly appreciated!  (Relating to
D3D would be great!)

Thank you,

Pai-Hung Chen