/*
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.

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

#include "r_local.h"

static finalvert_t fv[2][8];

void R_AliasProjectAndClipTestFinalVert( finalvert_t *fv );
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
================
*/
static void R_Alias_clip_z( finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out )
{
	float scale;

	scale = ( ALIAS_Z_CLIP_PLANE - pfv0->xyz[2] )
		/ ( pfv1->xyz[2] - pfv0->xyz[2] );

	out->xyz[0] = pfv0->xyz[0] + ( pfv1->xyz[0] - pfv0->xyz[0] ) * scale;
	out->xyz[1] = pfv0->xyz[1] + ( pfv1->xyz[1] - pfv0->xyz[1] ) * scale;
	out->xyz[2] = ALIAS_Z_CLIP_PLANE;

	out->s = pfv0->s + ( pfv1->s - pfv0->s ) * scale;
	out->t = pfv0->t + ( pfv1->t - pfv0->t ) * scale;
	out->l = pfv0->l + ( pfv1->l - pfv0->l ) * scale;

	R_AliasProjectAndClipTestFinalVert( out );
}

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

	if( pfv0->v >= pfv1->v )
	{
		scale = (float)( RI.aliasvrect.x - pfv0->u )
			/ ( pfv1->u - pfv0->u );
		out->u = pfv0->u + ( pfv1->u - pfv0->u ) * scale + 0.5f;
		out->v = pfv0->v + ( pfv1->v - pfv0->v ) * scale + 0.5f;
		out->s = pfv0->s + ( pfv1->s - pfv0->s ) * scale + 0.5f;
		out->t = pfv0->t + ( pfv1->t - pfv0->t ) * scale + 0.5f;
		out->l = pfv0->l + ( pfv1->l - pfv0->l ) * scale + 0.5f;
		out->zi = pfv0->zi + ( pfv1->zi - pfv0->zi ) * scale + 0.5f;
	}
	else
	{
		scale = (float)( RI.aliasvrect.x - pfv1->u )
			/ ( pfv0->u - pfv1->u );
		out->u = pfv1->u + ( pfv0->u - pfv1->u ) * scale + 0.5f;
		out->v = pfv1->v + ( pfv0->v - pfv1->v ) * scale + 0.5f;
		out->s = pfv1->s + ( pfv0->s - pfv1->s ) * scale + 0.5f;
		out->t = pfv1->t + ( pfv0->t - pfv1->t ) * scale + 0.5f;
		out->l = pfv1->l + ( pfv0->l - pfv1->l ) * scale + 0.5f;
		out->zi = pfv1->zi + ( pfv0->zi - pfv1->zi ) * scale + 0.5f;
	}
}

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

	if( pfv0->v >= pfv1->v )
	{
		scale = (float)( RI.aliasvrectright - pfv0->u )
			/ ( pfv1->u - pfv0->u );
		out->u = pfv0->u + ( pfv1->u - pfv0->u ) * scale + 0.5f;
		out->v = pfv0->v + ( pfv1->v - pfv0->v ) * scale + 0.5f;
		out->s = pfv0->s + ( pfv1->s - pfv0->s ) * scale + 0.5f;
		out->t = pfv0->t + ( pfv1->t - pfv0->t ) * scale + 0.5f;
		out->l = pfv0->l + ( pfv1->l - pfv0->l ) * scale + 0.5f;
		out->zi = pfv0->zi + ( pfv1->zi - pfv0->zi ) * scale + 0.5f;
	}
	else
	{
		scale = (float)( RI.aliasvrectright - pfv1->u )
			/ ( pfv0->u - pfv1->u );
		out->u = pfv1->u + ( pfv0->u - pfv1->u ) * scale + 0.5f;
		out->v = pfv1->v + ( pfv0->v - pfv1->v ) * scale + 0.5f;
		out->s = pfv1->s + ( pfv0->s - pfv1->s ) * scale + 0.5f;
		out->t = pfv1->t + ( pfv0->t - pfv1->t ) * scale + 0.5f;
		out->l = pfv1->l + ( pfv0->l - pfv1->l ) * scale + 0.5f;
		out->zi = pfv1->zi + ( pfv0->zi - pfv1->zi ) * scale + 0.5f;
	}
}

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

	if( pfv0->v >= pfv1->v )
	{
		scale = (float)( RI.aliasvrect.y - pfv0->v )
			/ ( pfv1->v - pfv0->v );
		out->u = pfv0->u + ( pfv1->u - pfv0->u ) * scale + 0.5f;
		out->v = pfv0->v + ( pfv1->v - pfv0->v ) * scale + 0.5f;
		out->s = pfv0->s + ( pfv1->s - pfv0->s ) * scale + 0.5f;
		out->t = pfv0->t + ( pfv1->t - pfv0->t ) * scale + 0.5f;
		out->l = pfv0->l + ( pfv1->l - pfv0->l ) * scale + 0.5f;
		out->zi = pfv0->zi + ( pfv1->zi - pfv0->zi ) * scale + 0.5f;
	}
	else
	{
		scale = (float)( RI.aliasvrect.y - pfv1->v )
			/ ( pfv0->v - pfv1->v );
		out->u = pfv1->u + ( pfv0->u - pfv1->u ) * scale + 0.5f;
		out->v = pfv1->v + ( pfv0->v - pfv1->v ) * scale + 0.5f;
		out->s = pfv1->s + ( pfv0->s - pfv1->s ) * scale + 0.5f;
		out->t = pfv1->t + ( pfv0->t - pfv1->t ) * scale + 0.5f;
		out->l = pfv1->l + ( pfv0->l - pfv1->l ) * scale + 0.5f;
		out->zi = pfv1->zi + ( pfv0->zi - pfv1->zi ) * scale + 0.5f;
	}
}

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

	if( pfv0->v >= pfv1->v )
	{
		scale = (float)( RI.aliasvrectbottom - pfv0->v )
			/ ( pfv1->v - pfv0->v );

		out->u = pfv0->u + ( pfv1->u - pfv0->u ) * scale + 0.5f;
		out->v = pfv0->v + ( pfv1->v - pfv0->v ) * scale + 0.5f;
		out->s = pfv0->s + ( pfv1->s - pfv0->s ) * scale + 0.5f;
		out->t = pfv0->t + ( pfv1->t - pfv0->t ) * scale + 0.5f;
		out->l = pfv0->l + ( pfv1->l - pfv0->l ) * scale + 0.5f;
		out->zi = pfv0->zi + ( pfv1->zi - pfv0->zi ) * scale + 0.5f;
	}
	else
	{
		scale = (float)( RI.aliasvrectbottom - pfv1->v )
			/ ( pfv0->v - pfv1->v );

		out->u = pfv1->u + ( pfv0->u - pfv1->u ) * scale + 0.5f;
		out->v = pfv1->v + ( pfv0->v - pfv1->v ) * scale + 0.5f;
		out->s = pfv1->s + ( pfv0->s - pfv1->s ) * scale + 0.5f;
		out->t = pfv1->t + ( pfv0->t - pfv1->t ) * scale + 0.5f;
		out->l = pfv1->l + ( pfv0->l - pfv1->l ) * scale + 0.5f;
		out->zi = pfv1->zi + ( pfv0->zi - pfv1->zi ) * scale + 0.5f;
	}
}

static 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].u < RI.aliasvrect.x )
				out[k].flags |= ALIAS_LEFT_CLIP;
			if( out[k].v < RI.aliasvrect.y )
				out[k].flags |= ALIAS_TOP_CLIP;
			if( out[k].u > RI.aliasvrectright )
				out[k].flags |= ALIAS_RIGHT_CLIP;
			if( out[k].v > RI.aliasvrectbottom )
				out[k].flags |= ALIAS_BOTTOM_CLIP;
			k++;
		}
		if( !flags )
		{
			out[k] = in[i];
			k++;
		}
	}

	return k;
}

/*
================
R_AliasClipTriangle
================
*/
void R_AliasClipTriangle( finalvert_t *index0, finalvert_t *index1, finalvert_t *index2 )
{
	int      i, k, pingpong;
	unsigned clipflags;

// copy vertexes and fix seam texture coordinates
	fv[0][0] = *index0;
	fv[0][1] = *index1;
	fv[0][2] = *index2;

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

	if( clipflags & ALIAS_Z_CLIP )
	{
		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].u < RI.aliasvrect.x )
			fv[pingpong][i].u = RI.aliasvrect.x;
		else if( fv[pingpong][i].u > RI.aliasvrectright )
			fv[pingpong][i].u = RI.aliasvrectright;

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

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

// draw triangles
	for( i = 1; i < k - 1; i++ )
	{
		aliastriangleparms.a = &fv[pingpong][0];
		aliastriangleparms.b = &fv[pingpong][i];
		aliastriangleparms.c = &fv[pingpong][i + 1];
		R_DrawTriangle();
	}
}