r_aclip.c

/*
Copyright (C) 1996-1997 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.

*/
// r_aclip.c: clip routines for drawing Alias models directly to the screen

#include "quakedef.h"
#include "r_local.h"
#include "d_local.h"

static finalvert_t		fv[2][8];
static auxvert_t		av[8];
#ifdef USEFPM
static auxvert_FPM_t	*avFPM[8];
#endif //USEFPM

void R_AliasProjectFinalVert (finalvert_t *fv, auxvert_t *av);
#ifdef USEFPM
void R_AliasProjectFinalVertFPM (finalvert_t *fv, auxvert_FPM_t *av);
#endif //USEFPM
void R_Alias_clip_top (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out);
void R_Alias_clip_bottom (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out);
void R_Alias_clip_left (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out);
void R_Alias_clip_right (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out);


/*
================
R_Alias_clip_z

pfv0 is the unclipped vertex, pfv1 is the z-clipped vertex
================
*/
void R_Alias_clip_z (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	float		scale;
	auxvert_t	*pav0, *pav1, avout;

	pav0 = &av[pfv0 - &fv[0][0]];
	pav1 = &av[pfv1 - &fv[0][0]];

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = (ALIAS_Z_CLIP_PLANE - pav0->fv[2]) /
				(pav1->fv[2] - pav0->fv[2]);
	
		avout.fv[0] = pav0->fv[0] + (pav1->fv[0] - pav0->fv[0]) * scale;
		avout.fv[1] = pav0->fv[1] + (pav1->fv[1] - pav0->fv[1]) * scale;
		avout.fv[2] = ALIAS_Z_CLIP_PLANE;
	
		out->v[2] =	pfv0->v[2] + (int)((pfv1->v[2] - pfv0->v[2]) * scale);
		out->v[3] =	pfv0->v[3] + (int)((pfv1->v[3] - pfv0->v[3]) * scale);
		out->v[4] =	pfv0->v[4] + (int)((pfv1->v[4] - pfv0->v[4]) * scale);
	}
	else
	{
		scale = (ALIAS_Z_CLIP_PLANE - pav1->fv[2]) /
				(pav0->fv[2] - pav1->fv[2]);
	
		avout.fv[0] = pav1->fv[0] + (int)((pav0->fv[0] - pav1->fv[0]) * scale);
		avout.fv[1] = pav1->fv[1] + (int)((pav0->fv[1] - pav1->fv[1]) * scale);
		avout.fv[2] = ALIAS_Z_CLIP_PLANE;
	
		out->v[2] =	pfv1->v[2] + (int)((pfv0->v[2] - pfv1->v[2]) * scale);
		out->v[3] =	pfv1->v[3] + (int)((pfv0->v[3] - pfv1->v[3]) * scale);
		out->v[4] =	pfv1->v[4] + (int)((pfv0->v[4] - pfv1->v[4]) * scale);
	}

	R_AliasProjectFinalVert (out, &avout);

	if (out->v[0] < r_refdef.aliasvrect.x)
		out->flags |= ALIAS_LEFT_CLIP;
	if (out->v[1] < r_refdef.aliasvrect.y)
		out->flags |= ALIAS_TOP_CLIP;
	if (out->v[0] > r_refdef.aliasvrectright)
		out->flags |= ALIAS_RIGHT_CLIP;
	if (out->v[1] > r_refdef.aliasvrectbottom)
		out->flags |= ALIAS_BOTTOM_CLIP;	
}

#ifdef USEFPM
void R_Alias_clip_z_FPM (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	fixedpoint_t	scale;
	auxvert_FPM_t	*pav0, *pav1, avout;

	pav0 = avFPM[pfv0 - &fv[0][0]];
	pav1 = avFPM[pfv1 - &fv[0][0]];

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = FPM_DIV(FPM_SUB(ALIAS_Z_CLIP_PLANE_FPM, pav0->fv[2]),
					FPM_SUB(pav1->fv[2], pav0->fv[2]));
	
		avout.fv[0] = FPM_TOLONG(FPM_ADD(pav0->fv[0], FPM_MUL(FPM_SUB(pav1->fv[0], pav0->fv[0]),scale)));
		avout.fv[1] = FPM_TOLONG(FPM_ADD(pav0->fv[1], FPM_MUL(FPM_SUB(pav1->fv[1], pav0->fv[1]), scale)));
		avout.fv[2] = ALIAS_Z_CLIP_PLANE;
	
		out->v[2] =	pfv0->v[2] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG(pfv1->v[2] - pfv0->v[2]), scale));
		out->v[3] =	pfv0->v[3] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG(pfv1->v[3] - pfv0->v[3]), scale));
		out->v[4] =	pfv0->v[4] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG(pfv1->v[4] - pfv0->v[4]), scale));
	}
	else
	{
		scale = FPM_DIV(FPM_SUB(ALIAS_Z_CLIP_PLANE_FPM, pav1->fv[2]),
					FPM_SUB(pav0->fv[2], pav1->fv[2]));
	
		avout.fv[0] = FPM_TOLONG(FPM_ADD(pav1->fv[0], FPM_MUL(FPM_SUB(pav0->fv[0], pav1->fv[0]),scale)));
		avout.fv[1] = FPM_TOLONG(FPM_ADD(pav1->fv[1], FPM_MUL(FPM_SUB(pav0->fv[1], pav1->fv[1]), scale)));
		avout.fv[2] = ALIAS_Z_CLIP_PLANE;
	
		out->v[2] =	pfv1->v[2] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG((pfv0->v[2] - pfv1->v[2])), scale));
		out->v[3] =	pfv1->v[3] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG(pfv0->v[3] - pfv1->v[3]), scale));
		out->v[4] =	pfv1->v[4] + FPM_TOLONG(FPM_MUL(FPM_FROMLONG(pfv0->v[4] - pfv1->v[4]), scale));
	}

	R_AliasProjectFinalVertFPM (out, &avout);

	if (out->v[0] < r_refdefFPM.aliasvrect.x)
		out->flags |= ALIAS_LEFT_CLIP;
	if (out->v[1] < r_refdefFPM.aliasvrect.y)
		out->flags |= ALIAS_TOP_CLIP;
	if (out->v[0] > r_refdefFPM.aliasvrectright)
		out->flags |= ALIAS_RIGHT_CLIP;
	if (out->v[1] > r_refdefFPM.aliasvrectbottom)
		out->flags |= ALIAS_BOTTOM_CLIP;	
}
#endif //USEFPM

#if	!id386

void R_Alias_clip_left (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	float		scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = (float)(r_refdef.aliasvrect.x - pfv0->v[0]) /
				(pfv1->v[0] - pfv0->v[0]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + (int)((pfv1->v[i] - pfv0->v[i])*scale + 0.5);
	}
	else
	{
		scale = (float)(r_refdef.aliasvrect.x - pfv1->v[0]) /
				(pfv0->v[0] - pfv1->v[0]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + (int)((pfv0->v[i] - pfv1->v[i])*scale + 0.5);
	}
}

#ifdef USEFPM
void R_Alias_clip_leftFPM (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	fixedpoint_t	scale;
	int				i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdef.aliasvrect.x - pfv0->v[0]),
				FPM_FROMLONG(pfv1->v[0] - pfv0->v[0]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = FPM_ADD3(FPM_FROMLONG(pfv0->v[i]), FPM_MUL(FPM_FROMLONG(pfv1->v[i] - pfv0->v[i]),scale), FPM_FROMFLOAT(0.5));
	}
	else
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdef.aliasvrect.x - pfv1->v[0]),
				FPM_FROMLONG(pfv0->v[0] - pfv1->v[0]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = FPM_ADD3(FPM_FROMLONG(pfv1->v[i]), FPM_MUL(FPM_FROMLONG(pfv0->v[i] - pfv1->v[i]),scale), FPM_FROMFLOAT(0.5));
	}
}
#endif //USEFPM

void R_Alias_clip_right (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out)
{
	float		scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = (float)(r_refdef.aliasvrectright - pfv0->v[0]) /
				(pfv1->v[0] - pfv0->v[0]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + (int)((pfv1->v[i] - pfv0->v[i])*scale + 0.5);
	}
	else
	{
		scale = (float)(r_refdef.aliasvrectright - pfv1->v[0]) /
				(pfv0->v[0] - pfv1->v[0]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + (int)((pfv0->v[i] - pfv1->v[i])*scale + 0.5);
	}
}

#ifdef USEFPM
void R_Alias_clip_rightFPM (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out)
{
	fixedpoint_t	scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrectright - pfv0->v[0]),
				FPM_FROMLONG(pfv1->v[0] - pfv0->v[0]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv1->v[i] - pfv0->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
	else
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrectright - pfv1->v[0]),
				FPM_FROMLONG(pfv0->v[0] - pfv1->v[0]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv0->v[i] - pfv1->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
}
#endif //USEFPM

void R_Alias_clip_top (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	float		scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = (float)(r_refdef.aliasvrect.y - pfv0->v[1]) /
				(pfv1->v[1] - pfv0->v[1]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + (int)((pfv1->v[i] - pfv0->v[i])*scale + 0.5);
	}
	else
	{
		scale = (float)(r_refdef.aliasvrect.y - pfv1->v[1]) /
				(pfv0->v[1] - pfv1->v[1]);
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + (int)((pfv0->v[i] - pfv1->v[i])*scale + 0.5);
	}
}

#ifdef USEFPM
void R_Alias_clip_topFPM (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
	fixedpoint_t	scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrect.y - pfv0->v[1]),
				FPM_FROMLONG(pfv1->v[1] - pfv0->v[1]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv1->v[i] - pfv0->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
	else
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrect.y - pfv1->v[1]),
				FPM_FROMLONG(pfv0->v[1] - pfv1->v[1]));
		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv0->v[i] - pfv1->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
}
#endif //USEFPM

void R_Alias_clip_bottom (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out)
{
	float		scale;
	int			i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = (float)(r_refdef.aliasvrectbottom - pfv0->v[1]) /
				(pfv1->v[1] - pfv0->v[1]);

		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + (int)((pfv1->v[i] - pfv0->v[i])*scale + 0.5);
	}
	else
	{
		scale = (float)(r_refdef.aliasvrectbottom - pfv1->v[1]) /
				(pfv0->v[1] - pfv1->v[1]);

		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + (int)((pfv0->v[i] - pfv1->v[i])*scale + 0.5);
	}
}

#ifdef USEFPM
void R_Alias_clip_bottomFPM (finalvert_t *pfv0, finalvert_t *pfv1,
	finalvert_t *out)
{
	fixedpoint_t	scale;
	int				i;

	if (pfv0->v[1] >= pfv1->v[1])
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrectbottom - pfv0->v[1]),
				FPM_FROMLONG(pfv1->v[1] - pfv0->v[1]));

		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv0->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv1->v[i] - pfv0->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
	else
	{
		scale = FPM_DIV(FPM_FROMLONG(r_refdefFPM.aliasvrectbottom - pfv1->v[1]),
				FPM_FROMLONG(pfv0->v[1] - pfv1->v[1]));

		for (i=0 ; i<6 ; i++)
			out->v[i] = pfv1->v[i] + FPM_TOLONG(FPM_ADD(FPM_MUL(FPM_FROMLONG(pfv0->v[i] - pfv1->v[i]),scale), FPM_FROMFLOAT(0.5)));
	}
}
#endif //USEFPM
#endif


int R_AliasClip (finalvert_t *in, finalvert_t *out, int flag, int count,
	void(*clip)(finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out) )
{
	int			i,j,k;
	int			flags, oldflags;
	
	j = count-1;
	k = 0;
	for (i=0 ; i<count ; j = i, i++)
	{
		oldflags = in[j].flags & flag;
		flags = in[i].flags & flag;

		if (flags && oldflags)
			continue;
		if (oldflags ^ flags)
		{
			clip (&in[j], &in[i], &out[k]);
			out[k].flags = 0;
			if (out[k].v[0] < r_refdef.aliasvrect.x)
				out[k].flags |= ALIAS_LEFT_CLIP;
			if (out[k].v[1] < r_refdef.aliasvrect.y)
				out[k].flags |= ALIAS_TOP_CLIP;
			if (out[k].v[0] > r_refdef.aliasvrectright)
				out[k].flags |= ALIAS_RIGHT_CLIP;
			if (out[k].v[1] > r_refdef.aliasvrectbottom)
				out[k].flags |= ALIAS_BOTTOM_CLIP;	
			k++;
		}
		if (!flags)
		{
			out[k] = in[i];
			k++;
		}
	}
	
	return k;
}

#ifdef USEFPM
int R_AliasClipFPM (finalvert_t *in, finalvert_t *out, int flag, int count,
	void(*clip)(finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out) )
{
	int			i,j,k;
	int			flags, oldflags;
	
	j = count-1;
	k = 0;
	for (i=0 ; i<count ; j = i, i++)
	{
		oldflags = in[j].flags & flag;
		flags = in[i].flags & flag;

		if (flags && oldflags)
			continue;
		if (oldflags ^ flags)
		{
			clip (&in[j], &in[i], &out[k]);
			out[k].flags = 0;
			if (out[k].v[0] < r_refdefFPM.aliasvrect.x)
				out[k].flags |= ALIAS_LEFT_CLIP;
			if (out[k].v[1] < r_refdefFPM.aliasvrect.y)
				out[k].flags |= ALIAS_TOP_CLIP;
			if (out[k].v[0] > r_refdefFPM.aliasvrectright)
				out[k].flags |= ALIAS_RIGHT_CLIP;
			if (out[k].v[1] > r_refdefFPM.aliasvrectbottom)
				out[k].flags |= ALIAS_BOTTOM_CLIP;	
			k++;
		}
		if (!flags)
		{
			out[k] = in[i];
			k++;
		}
	}
	
	return k;
}
#endif //USEFPM
/*
================
R_AliasClipTriangle
================
*/
void R_AliasClipTriangle (mtriangle_t *ptri)
{
	int				i, k, pingpong;
	mtriangle_t		mtri;
	unsigned		clipflags;

// copy vertexes and fix seam texture coordinates
	if (ptri->facesfront)
	{
		fv[0][0] = pfinalverts[ptri->vertindex[0]];
		fv[0][1] = pfinalverts[ptri->vertindex[1]];
		fv[0][2] = pfinalverts[ptri->vertindex[2]];
	}
	else
	{
		for (i=0 ; i<3 ; i++)
		{
			fv[0][i] = pfinalverts[ptri->vertindex[i]];
	
			if (!ptri->facesfront && (fv[0][i].flags & ALIAS_ONSEAM) )
				fv[0][i].v[2] += r_affinetridesc.seamfixupX16;
		}
	}

// clip
	clipflags = fv[0][0].flags | fv[0][1].flags | fv[0][2].flags;

	if (clipflags & ALIAS_Z_CLIP)
	{
		for (i=0 ; i<3 ; i++)
			av[i] = pauxverts[ptri->vertindex[i]];

		k = R_AliasClip (fv[0], fv[1], ALIAS_Z_CLIP, 3, R_Alias_clip_z);
		if (k == 0)
			return;

		pingpong = 1;
		clipflags = fv[1][0].flags | fv[1][1].flags | fv[1][2].flags;
	}
	else
	{
		pingpong = 0;
		k = 3;
	}

	if (clipflags & ALIAS_LEFT_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_LEFT_CLIP, k, R_Alias_clip_left);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_RIGHT_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_RIGHT_CLIP, k, R_Alias_clip_right);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_BOTTOM_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_BOTTOM_CLIP, k, R_Alias_clip_bottom);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_TOP_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_TOP_CLIP, k, R_Alias_clip_top);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	for (i=0 ; i<k ; i++)
	{
		if (fv[pingpong][i].v[0] < r_refdef.aliasvrect.x)
			fv[pingpong][i].v[0] = r_refdef.aliasvrect.x;
		else if (fv[pingpong][i].v[0] > r_refdef.aliasvrectright)
			fv[pingpong][i].v[0] = r_refdef.aliasvrectright;

		if (fv[pingpong][i].v[1] < r_refdef.aliasvrect.y)
			fv[pingpong][i].v[1] = r_refdef.aliasvrect.y;
		else if (fv[pingpong][i].v[1] > r_refdef.aliasvrectbottom)
			fv[pingpong][i].v[1] = r_refdef.aliasvrectbottom;

		fv[pingpong][i].flags = 0;
	}

// draw triangles
	mtri.facesfront = ptri->facesfront;
	r_affinetridesc.ptriangles = &mtri;
	r_affinetridesc.pfinalverts = fv[pingpong];

// FIXME: do all at once as trifan?
	mtri.vertindex[0] = 0;
	for (i=1 ; i<k-1 ; i++)
	{
		mtri.vertindex[1] = i;
		mtri.vertindex[2] = i+1;
		D_PolysetDraw ();
	}
}

#ifdef USEFPM
void R_AliasClipTriangleFPM(mtriangle_t *ptri)
{
	int				i, k, pingpong;
	mtriangle_t		mtri;
	unsigned		clipflags;

// copy vertexes and fix seam texture coordinates
	if (ptri->facesfront)
	{
		fv[0][0] = pfinalverts[ptri->vertindex[0]];
		fv[0][1] = pfinalverts[ptri->vertindex[1]];
		fv[0][2] = pfinalverts[ptri->vertindex[2]];
	}
	else
	{
		for (i=0 ; i<3 ; i++)
		{
			fv[0][i] = pfinalverts[ptri->vertindex[i]];
	
			if (!ptri->facesfront && (fv[0][i].flags & ALIAS_ONSEAM) )
				fv[0][i].v[2] += r_affinetridesc.seamfixupX16;
		}
	}

// clip
	clipflags = fv[0][0].flags | fv[0][1].flags | fv[0][2].flags;

	if (clipflags & ALIAS_Z_CLIP)
	{
		for (i=0 ; i<3 ; i++)
			avFPM[i] = &pauxvertsFPM[ptri->vertindex[i]];

		k = R_AliasClip (fv[0], fv[1], ALIAS_Z_CLIP, 3, R_Alias_clip_z_FPM);
		if (k == 0)
			return;

		pingpong = 1;
		clipflags = fv[1][0].flags | fv[1][1].flags | fv[1][2].flags;
	}
	else
	{
		pingpong = 0;
		k = 3;
	}

	if (clipflags & ALIAS_LEFT_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_LEFT_CLIP, k, R_Alias_clip_left);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_RIGHT_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_RIGHT_CLIP, k, R_Alias_clip_right);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_BOTTOM_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_BOTTOM_CLIP, k, R_Alias_clip_bottom);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	if (clipflags & ALIAS_TOP_CLIP)
	{
		k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1],
							ALIAS_TOP_CLIP, k, R_Alias_clip_top);
		if (k == 0)
			return;

		pingpong ^= 1;
	}

	for (i=0 ; i<k ; i++)
	{
		if (fv[pingpong][i].v[0] < r_refdefFPM.aliasvrect.x)
			fv[pingpong][i].v[0] = r_refdefFPM.aliasvrect.x;
		else if (fv[pingpong][i].v[0] > r_refdefFPM.aliasvrectright)
			fv[pingpong][i].v[0] = r_refdefFPM.aliasvrectright;

		if (fv[pingpong][i].v[1] < r_refdefFPM.aliasvrect.y)
			fv[pingpong][i].v[1] = r_refdefFPM.aliasvrect.y;
		else if (fv[pingpong][i].v[1] > r_refdefFPM.aliasvrectbottom)
			fv[pingpong][i].v[1] = r_refdefFPM.aliasvrectbottom;

		fv[pingpong][i].flags = 0;
	}

// draw triangles
	mtri.facesfront = ptri->facesfront;
	r_affinetridesc.ptriangles = &mtri;
	r_affinetridesc.pfinalverts = fv[pingpong];

// FIXME: do all at once as trifan?
	mtri.vertindex[0] = 0;
	for (i=1 ; i<k-1 ; i++)
	{
		mtri.vertindex[1] = i;
		mtri.vertindex[2] = i+1;
		D_PolysetDraw ();
	}
}
#endif //USEFPM