Re: [AD] scanline extension

[Bertrand Coconnier <bcoconni@xxxxxxxxxx>]

tom st denis wrote :
> 
> --- Bertrand Coconnier <bcoconni@xxxxxxxxxx> wrote:
> > tom st denis wrote :
> > >
> > > ok I gave it more thought... lets use this...
> > >
> > > typedef struct {
> > >    BITMAP *dest,    /* destination bitmap */
> > >           *txt;     /* texture map if any */
> > >    int    x1, x2,   /* x start and end coords */
> > >           y,        /* line to draw on */
> > >           u1, u2,   /* texture x start/end */
> > >           v1, v2,   /* texture y start/end */
> > >           c1, c2;   /* color start/end */
> > >    float  z1,z2;    /* scanline start/end Z */
> > > } scanlineinfo;
> > >
> > > void draw_scanline(scanlineinfo *sli);
> > >
> > > Then you tell allegro
> > >
> > > add_scanline_drawer(&draw_scanline, MYTYPE)
> > >
> > > Where MYTYPE is an integer.
> >
> > You are reinventing the wheel :-) If you take a look at iscan.s (ASM
> > rendering func) or cscan.h (C rendering func) you'll see that :
> >
> > 1. The struct you are talking about already exists : it is called
> > POLYGON_SEGMENT (declared in private headers file
> > include/allegro/aintern.h)
> > 2. The actual rendering functions are declared this way :
> >
> > void _poly_scanline_the_mode(unsigned long addr, int w,
> > POLYGON_SEGMENT
> > *info)
> >
> > where - addr is the BITMAP address where the scanline will be
> > rendered
> >       - w is the scanline width
> >       - info is the structure which contains (u, du, v, dv, c, dc,
> > texture address, etc...)
> 
> So can support for user renderer be added?

Yep ! The general idea is useful. IMHO we would need to :

1. create the scanline renderer type : 

typedef void SCANLINE_FUNC(unsigned long, int, POLYGON_SEGMENT*); 

and a structure :

typedef struct SCANLINE_MAP {
   SCANLINE_FUNC func8;     /* 8 bpp scanline renderer */
   SCANLINE_FUNC func15;    /* 15 bpp scanline renderer */
   SCANLINE_FUNC func16;    /* 16 bpp scanline renderer */
   SCANLINE_FUNC func24;    /* 24 bpp scanline renderer */
   SCANLINE_FUNC func32;    /* 32 bpp scanline renderer */
   SCANLINE_FUNC zfunc8;
   SCANLINE_FUNC zfunc15;
   SCANLINE_FUNC zfunc16;   /* same as before + Z-buffer support */
   SCANLINE_FUNC zfunc24;
   SCANLINE_FUNC zfunc32;
} SCANLINE_MAP;

2. add a new function to the lib which may look like :

int add_scanline_drawer(SCANLINE_MAP* my_scan_map, int mytype, int
interp_var)

where (mytype) is the new type handled by 'my_scan_map' map and
(interp_var) describes the variables which need to be interpolated (see
arrays 'polytype_interp_pal' and 'polytype_interp_tc' in poly3d.c).

3. This function would update 'polytype_info' arrays in poly3d.c as well
as the 'flag_table' in clip3d.c and clip3d_f.c some other minor things.

	Bertrand.