r_part.c

Quake 2 Source code for students by Theerthan You can also download from idsoftwares.com

	** which also means clamping to a min and max
	*/
	//	pix = izi >> d_pix_shift;
	__asm xor edx, edx
	__asm mov dx, izi
	__asm mov ecx, d_pix_shift
	__asm shr dx, cl

	//	if (pix < d_pix_min)
	//		pix = d_pix_min;
	__asm cmp edx, d_pix_min
	__asm jge check_pix_max
	__asm mov edx, d_pix_min
	__asm jmp skip_pix_clamp

	//	else if (pix > d_pix_max)
	//		pix = d_pix_max;
check_pix_max:
	__asm cmp edx, d_pix_max
	__asm jle skip_pix_clamp
	__asm mov edx, d_pix_max

skip_pix_clamp:

	/*
	** render the appropriate pixels
	**
	** ECX = count (used for inner loop)
	** EDX = count (used for outer loop)
	** ESI = zbuffer
	** EDI = framebuffer
	*/
	__asm mov ecx, edx

	__asm cmp ecx, 1
	__asm ja  over

over:

	/*
	** at this point:
	**
	** ECX = count
	*/
	__asm push ecx
	__asm push edi
	__asm push esi

top_of_pix_vert_loop:

top_of_pix_horiz_loop:

	//	for ( ; count ; count--, pz += d_zwidth, pdest += screenwidth)
	//	{
	//		for (i=0 ; i<pix ; i++)
	//		{
	//			if (pz[i] <= izi)
	//			{
	//				pdest[i] = blendparticle( color, pdest[i] );
	//			}
	//		}
	//	}
	__asm xor   eax, eax

	__asm mov   ax, word ptr [esi]

	__asm cmp   ax, izi
	__asm jg    end_of_horiz_loop

#if ENABLE_ZWRITES_FOR_PARTICLES
  	__asm mov   bp, izi
  	__asm mov   word ptr [esi], bp
#endif

	__asm mov   eax, partparms.color

	__asm call  [blendfunc]

	__asm add   edi, 1
	__asm add   esi, 2

end_of_horiz_loop:

	__asm dec   ecx
	__asm jnz   top_of_pix_horiz_loop

	__asm pop   esi
	__asm pop   edi

	__asm mov   ebp, d_zwidth
	__asm shl   ebp, 1

	__asm add   esi, ebp
	__asm add   edi, [r_screenwidth]

	__asm pop   ecx
	__asm push  ecx

	__asm push  edi
	__asm push  esi

	__asm dec   edx
	__asm jnz   top_of_pix_vert_loop

	__asm pop   ecx
	__asm pop   ecx
	__asm pop   ecx

end:
	__asm pop edi
	__asm pop esi
	__asm mov ebp, ebpsave
	__asm ret
}

#else

static byte BlendParticle33( int pcolor, int dstcolor )
{
	return vid.alphamap[pcolor + dstcolor*256];
}

static byte BlendParticle66( int pcolor, int dstcolor )
{
	return vid.alphamap[pcolor*256+dstcolor];
}

static byte BlendParticle100( int pcolor, int dstcolor )
{
	dstcolor = dstcolor;
	return pcolor;
}

/*
** 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.
*/
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;
	byte  (*blendparticle)( int, int );

	/*
	** 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;

	/*
	** bind the blend function pointer to the appropriate blender
	*/
	if ( level == PARTICLE_33 )
		blendparticle = BlendParticle33;
	else if ( level == PARTICLE_66 )
		blendparticle = BlendParticle66;
	else 
		blendparticle = BlendParticle100;

	/*
	** 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;
    }
}

#endif	// !id386

/*
** 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;
	extern unsigned long fpu_sp24_cw, fpu_chop_cw;

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

#if id386 && !defined __linux__
	__asm fldcw word ptr [fpu_sp24_cw]
#endif

	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;

#if id386 && !defined __linux__
		if ( i < r_newrefdef.num_particles-1 )
			s_prefetch_address = ( unsigned int ) ( p + 1 );
		else
			s_prefetch_address = ( unsigned int ) r_newrefdef.particles;
#endif

		R_DrawParticle();
	}

#if id386 && !defined __linux__
	__asm fldcw word ptr [fpu_chop_cw]
#endif

}