Re: [Plib-users] Messing with ssg

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

Will Newton wrote:
> 
> I've been writing some cell shading code (Jet Set Radio style :) and I'm
> trying to hook it into ssg as a simple way to debug it.

I've never heard of 'cell shading' - or 'Jet Set Radio' - please enlighten me!

> In essence I need to override the drawing code of a particular object. It
> looks like it probably isn't possible, but can anyone see a way to do
> this?

Well, there are several ways:

* Write a derived class of ssgLeaf or ssgVtxTable that replaces the 'draw'
  virtual member function with whatever you need to do. You'll have to take
  on responsibility for calling pre- and post-Draw callbacks and working with
  the ssgState management system to get the states setup.

* As above - but only override the 'fraw_geometry' member function.  Then
  *all* you have to do is draw the polygons - the underlying native SSG
  class will do everything else.

* Write a pre-Draw callback for an existing class - but have it do all the
  rendering and return FALSE - which will tell SSG *not* to go and draw
  the object itself.

The third way avoids SSG's state setup code though - so you'd have to
set up (and restore) the OpenGL state before and after your rendering.

The first way is therefore considerably superior - but maybe more
than you want to do for a quick hack.

The second way is probably what you need.  Just look at:

   void ssgVtxTable::draw_geometry()

...in src/ssg/ssgVtxTable.cxx - use that as an example.

...and of course, when it's all working - CONTRIBUTE IT!

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