Date: Tue, 18 Jun 1996 17:10:41 -0500
From: Jim Bucher <jim@gcchem.com>
To: quake-dev@gamers.org
Subject: Re: BSP edge list
Greg Lewis wrote:
>
> I've got a question concerning the edge lists. I'm iterating the
> surface data to find and draw all of the edges onscreen. From the Qspec
> 3.1 I assumed that if I go through the List of Edges and take the sign
> into account, the edges will always be given in a counterclockwise order
> around the surface. And, thus I would only need to compute half of the
> vertices (since the start of one is the end of the next edge). However,
> while going through the list it looks like the end of one edge is NOT
> always the same position as the start of the next edge. (I believe the
> first time this happens is surface 9, edge 1.) Can anyone confirm/deny
> this? It seems to me like the edges should form a closed polygon, i.e.
> each vertex is the start of one line and the end of another (after taking
> the sign flip into account).
The edges do not always form a closed polygon. They surfaces are also not
always convex, and sometimes they have holes in them. For instance on
map test1 the room with the lava and yellow armor has a floor with holes
in it. This floor is all one surface. If I remember right the edges
are comprised of indicies into a vertex list. So you should be able to
transform the verticies in the vertex list and avoid transforming the
same vertex twice.