Re: [Plib-users] SSG for 3ds and ASE

[Steve B. <sjb...@ai...>]

> Dave McClurg wrote:
> 
> > Can you detect when you get an old-style file and generate
> > normals like ssgLoadAC does?  (AC3D files *never* contain
> > normals).
> 
> ssgLoadAC doesn't generate normals.  That happens in ssgOptimiser
> (void OptVertexList::makeNormals()).  This code crashes when it runs
> on an ASE model.  What is worse is that ASE models create indexed
> ssgVtxArrays and shared verticies imply shared normals.
>  ssgOptimiser creates face normals instead of vertex normals.
>  This means a shared vertex may require two *different* normals
> and the indexed ssgVtxArray would have to be rebuilt.  ugh.

Yikes!  You understand this unholy mess better than I do!

We really need to stop and think about "Loader Service Routines" before
we go too much further down the loader writing curve.

I'd expect nearly any loader to benefit from:

  * Polygon decimation to triangles.
  * Optimal Tristrip creation.
  * Parser support.
  * Callbacks for applications that need to extend the
    file format via comment fields, etc.
  * Callbacks for applications that need to build their
    own ssgStates.
  * Surface normal generation.
  * Degenerate triangle/vertex removal.
  * Flattening (multiplying out the matrices in ssgTransform
    nodes and doing a one-time transform of vertices in the
    leaf node)
  * Degenerate group removal (eg deleting ssgBranch nodes with
    either one or zero children - but only if the node isn't
    known to the application - or a derived class of ssgBranch).
  * ssgState sharing between leaf nodes.
  * Texture coordinate size reduction.

...and probably a lot more.

Back when it looked like AC3D and maybe one other might be the only
loaders there would ever be, I didn't take too much time to modularize
this stuff.  But with the likelyhood that we could end up with a dozen
or more loaders eventually (especially since the advent of PPE), we need
to seriously look into this.

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