/*
Copyright (C) 1997-2001 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
#include "sw_local.h"

vec3_t r_pright, r_pup, r_ppn;

#define PARTICLE_33     0
#define PARTICLE_66     1
#define PARTICLE_OPAQUE 2

typedef struct
{
	particle_t *particle;
	int         level;
	int         color;
} partparms_t;

static partparms_t partparms;

/*
** R_DrawParticle
**
** Yes, this is amazingly slow, but it's the C reference
** implementation and should be both robust and vaguely
** understandable.  The only time this path should be
** executed is if we're debugging on x86 or if we're
** recompiling and deploying on a non-x86 platform.
**
** To minimize error and improve readability I went the 
** function pointer route.  This exacts some overhead, but
** it pays off in clean and easy to understand code.
*/
static void R_DrawParticle( void )
{
	particle_t *pparticle = partparms.particle;
	int         level     = partparms.level;
	vec3_t	local, transformed;
	float	zi;
	byte	*pdest;
	short	*pz;
	int      color = pparticle->color;
	int		i, izi, pix, count, u, v;

	/*
	** transform the particle
	*/
	VectorSubtract (pparticle->origin, r_origin, local);

	transformed[0] = DotProduct(local, r_pright);
	transformed[1] = DotProduct(local, r_pup);
	transformed[2] = DotProduct(local, r_ppn);		

	if (transformed[2] < PARTICLE_Z_CLIP)
		return;

	/*
	** project the point
	*/
	// FIXME: preadjust xcenter and ycenter
	zi = 1.0 / transformed[2];
	u = (int)(xcenter + zi * transformed[0] + 0.5);
	v = (int)(ycenter - zi * transformed[1] + 0.5);

	if ((v > d_vrectbottom_particle) || 
		(u > d_vrectright_particle) ||
		(v < d_vrecty) ||
		(u < d_vrectx))
	{
		return;
	}

	/*
	** compute addresses of zbuffer, framebuffer, and 
	** compute the Z-buffer reference value.
	*/
	pz = d_pzbuffer + (d_zwidth * v) + u;
	pdest = d_viewbuffer + d_scantable[v] + u;
	izi = (int)(zi * 0x8000);

	/*
	** determine the screen area covered by the particle,
	** which also means clamping to a min and max
	*/
	pix = izi >> d_pix_shift;
	if (pix < d_pix_min)
		pix = d_pix_min;
	else if (pix > d_pix_max)
		pix = d_pix_max;

	/*
	** render the appropriate pixels
	*/
	count = pix;

    switch (level) {
    case PARTICLE_33 :
        for ( ; count ; count--, pz += d_zwidth, pdest += r_screenwidth)
        {
//FIXME--do it in blocks of 8?
            for (i=0 ; i<pix ; i++)
            {
                if (pz[i] <= izi)
                {
                    pz[i]    = izi;
                    pdest[i] = vid.alphamap[color + ((int)pdest[i]<<8)];
                }
            }
        }
        break;

    case PARTICLE_66 :
        for ( ; count ; count--, pz += d_zwidth, pdest += r_screenwidth)
        {
            for (i=0 ; i<pix ; i++)
            {
                if (pz[i] <= izi)
                {
                    pz[i]    = izi;
                    pdest[i] = vid.alphamap[(color<<8) + (int)pdest[i]];
                }
            }
        }
        break;

    default:  //100
        for ( ; count ; count--, pz += d_zwidth, pdest += r_screenwidth)
        {
            for (i=0 ; i<pix ; i++)
            {
                if (pz[i] <= izi)
                {
                    pz[i]    = izi;
                    pdest[i] = color;
                }
            }
        }
        break;
    }
}

/*
** R_DrawParticles
**
** Responsible for drawing all of the particles in the particle list
** throughout the world.  Doesn't care if we're using the C path or
** if we're using the asm path, it simply assigns a function pointer
** and goes.
*/
void R_DrawParticles (void)
{
	particle_t *p;
	int         i;

	VectorScale( vright, xscaleshrink, r_pright );
	VectorScale( vup, yscaleshrink, r_pup );
	VectorCopy( vpn, r_ppn );

	for (p=r_newrefdef.particles, i=0 ; i<r_newrefdef.num_particles ; i++,p++)
	{

		if ( p->alpha > 0.66 )
			partparms.level = PARTICLE_OPAQUE;
		else if ( p->alpha > 0.33 )
			partparms.level = PARTICLE_66;
		else
			partparms.level = PARTICLE_33;

		partparms.particle = p;
		partparms.color    = p->color;

		R_DrawParticle();
	}
}