/*
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.

*/
// gl_warp.c -- sky and water polygons

#include "quakedef.h"
#include "neh.h"

extern	model_t	*loadmodel;

static int	  sky_width, sky_height;

int		  solidskytexture;
int		  alphaskytexture;
float		  speedscale;		// for top sky and bottom sky

static msurface_t *warpface;

static void BoundPoly (int numverts, float *verts, vec3_t mins, vec3_t maxs)
{
	int		i, j;
	float	*v;

	mins[0] = mins[1] = mins[2] = 9999;
	maxs[0] = maxs[1] = maxs[2] = -9999;
	v = verts;
	for (i=0 ; i<numverts ; i++)
		for (j=0 ; j<3 ; j++, v++)
		{
			if (*v < mins[j])
				mins[j] = *v;
			if (*v > maxs[j])
				maxs[j] = *v;
		}
}

static unsigned RecursLevel;

static void SubdividePolygon (int numverts, float *verts)
{
	int	    i, j, k;
	vec3_t	    mins, maxs;
	float	    m;
	float	    *v;
	vec3_t	    front[64], back[64];
	int	    f, b;
	float	    dist[64];
	float	    frac;
	glpoly_t    *poly;
	float	    s, t, subdivide;

	if (++RecursLevel > 128) // 16 seems enough and 512 might create stack overflow
		Sys_Error ("SubdividePolygon: excessive tree depth");

	if (numverts > 60)
		Sys_Error ("SubdividePolygon: excessive numverts %i", numverts);

	subdivide = gl_subdivide_size.value;

	if (subdivide < 32)
		subdivide = 32; // Avoid low subdivide values

	BoundPoly (numverts, verts, mins, maxs);

	for (i=0 ; i<3 ; i++)
	{
		m = (mins[i] + maxs[i]) * 0.5;
		m = subdivide * floor (m/subdivide + 0.5);
		if (maxs[i] - m < 8)
			continue;
		if (m - mins[i] < 8)
			continue;

		// cut it
		v = verts + i;
		for (j=0 ; j<numverts ; j++, v+= 3)
			dist[j] = *v - m;

		// wrap cases
		dist[j] = dist[0];
		v-=i;
		VectorCopy (verts, v);

		f = b = 0;
		v = verts;
		for (j=0 ; j<numverts ; j++, v+= 3)
		{
			if (dist[j] >= 0)
			{
				VectorCopy (v, front[f]);
				f++;
			}
			if (dist[j] <= 0)
			{
				VectorCopy (v, back[b]);
				b++;
			}
			if (dist[j] == 0 || dist[j+1] == 0)
				continue;
			if ( (dist[j] > 0) != (dist[j+1] > 0) )
			{
				// clip point
				frac = dist[j] / (dist[j] - dist[j+1]);
				for (k=0 ; k<3 ; k++)
					front[f][k] = back[b][k] = v[k] + frac*(v[3+k] - v[k]);
				f++;
				b++;
			}
		}

		SubdividePolygon (f, front[0]);
		SubdividePolygon (b, back[0]);
		--RecursLevel;
		return;
	}

	poly = Hunk_Alloc (sizeof(glpoly_t) + (numverts-4) * VERTEXSIZE*sizeof(float));
	poly->next = warpface->polys;
	warpface->polys = poly;
	poly->numverts = numverts;
	for (i=0 ; i<numverts ; i++, verts+= 3)
	{
		VectorCopy (verts, poly->verts[i]);
		s = DotProduct (verts, warpface->texinfo->vecs[0]);
		t = DotProduct (verts, warpface->texinfo->vecs[1]);
		poly->verts[i][3] = s;
		poly->verts[i][4] = t;
	}
	
	--RecursLevel;
}

/*
================
GL_SubdivideSurface

Breaks a polygon up along axial 64 unit
boundaries so that turbulent and sky warps
can be done reasonably.
================
*/
void GL_SubdivideSurface (msurface_t *fa)
{
	vec3_t		verts[64];
	int			numverts;
	int			i;
	int			lindex;
	float		*vec;
	texture_t	*t;

	warpface = fa;

	//
	// convert edges back to a normal polygon
	//
	numverts = 0;
	for (i=0 ; i<fa->numedges ; i++)
	{
		lindex = loadmodel->surfedges[fa->firstedge + i];

		if (lindex > 0)
			vec = loadmodel->vertexes[loadmodel->edges[lindex].v[0]].position;
		else
			vec = loadmodel->vertexes[loadmodel->edges[-lindex].v[1]].position;
		
		if (numverts >= 64)
			Sys_Error ("GL_SubdivideSurface: excessive numverts %i", numverts);

		VectorCopy (vec, verts[numverts]);
		numverts++;
	}

	RecursLevel = 0;
	SubdividePolygon (numverts, verts[0]);
}

//=========================================================



// speed up sin calculations - Ed
float	turbsin[] =
{
        #include "gl_warp_sin.h"
};
#define TURBSCALE (256.0 / (2 * M_PI))

static void EmitFlatPoly (msurface_t *fa)
{
	glpoly_t	*p;
	float		*v;
	int		i;

	for (p = fa->polys ; p ; p = p->next)
	{
		glBegin (GL_POLYGON);
		for (i = 0, v = p->verts[0] ; i < p->numverts ; i++, v += VERTEXSIZE)
			glVertex3fv (v);
		glEnd ();
	}
}

/*
=============
EmitWaterPolys

Does a water warp on the pre-fragmented glpoly_t chain
=============
*/
void EmitWaterPolys (msurface_t *fa)
{
	glpoly_t	*p;
	float		*v;
	int			i;
	float		s, t, os, ot;

        vec3_t          nv;



	for (p=fa->polys ; p ; p=p->next)
	{
		glBegin (GL_POLYGON);
		for (i=0,v=p->verts[0] ; i<p->numverts ; i++, v+=VERTEXSIZE)
		{
			os = v[3];
			ot = v[4];

			s = os + turbsin[(int)((ot*0.125+realtime) * TURBSCALE) & 255];
			s *= (1.0/64);

			t = ot + turbsin[(int)((os*0.125+realtime) * TURBSCALE) & 255];
			t *= (1.0/64);

			glTexCoord2f (s, t);

			if(r_waterripple.value) {
				nv[0] = v[0];
				nv[1] = v[1];
				nv[2] = v[2] + r_waterripple.value*sin(v[0]*0.05+realtime*3)*sin(v[2]*0.05+realtime*3);
				glVertex3fv (nv);
			} else {
				glVertex3fv (v);
			}

		}
		glEnd ();
	}
}

/*
=============
EmitSkyPolys
=============
*/
void EmitSkyPolys (msurface_t *fa)
{
	glpoly_t	*p;
	float		*v;
	int			i;
	float	s, t;
	vec3_t	dir;
	float	length;

	for (p=fa->polys ; p ; p=p->next)
	{
		glBegin (GL_POLYGON);
		for (i=0,v=p->verts[0] ; i<p->numverts ; i++, v+=VERTEXSIZE)
		{
			VectorSubtract (v, r_origin, dir);
			dir[2] *= 3;	// flatten the sphere

			length = dir[0]*dir[0] + dir[1]*dir[1] + dir[2]*dir[2];
			length = sqrt (length);
			length = 6*63/length;

			dir[0] *= length;
			dir[1] *= length;

			s = (speedscale + dir[0]) * (1.0/128);
			t = (speedscale + dir[1]) * (1.0/128);

			glTexCoord2f (s, t);
			glVertex3fv (v);
		}
		glEnd ();
	}
}

/*
===============
EmitBothSkyLayers

Does a sky warp on the pre-fragmented glpoly_t chain
This will be called for brushmodels, the world
will have them chained together.
===============
*/
void EmitBothSkyLayers (msurface_t *fa)
{
	int			i;
	int			lindex;
	float		*vec;

	GL_DisableMultitexture();

	GL_Bind (solidskytexture);
	speedscale = realtime*8;
	speedscale -= (int)speedscale & ~127 ;

	EmitSkyPolys (fa);

	glEnable (GL_BLEND);
	GL_Bind (alphaskytexture);
	speedscale = realtime*16;
	speedscale -= (int)speedscale & ~127 ;

	EmitSkyPolys (fa);

	glDisable (GL_BLEND);
}

/*
=================================================================

  PCX Loading

=================================================================
*/

typedef struct
{
    char	manufacturer;
    char	version;
    char	encoding;
    char	bits_per_pixel;
    unsigned short	xmin,ymin,xmax,ymax;
    unsigned short	hres,vres;
    unsigned char	palette[48];
    char	reserved;
    char	color_planes;
    unsigned short	bytes_per_line;
    unsigned short	palette_type;
    char	filler[58];
    unsigned 	data;			// unbounded
} pcx_t;

static byte *pcx_rgb;

/*
============
LoadPCX
============
*/
static void LoadPCX (FILE *f)
{
	pcx_t	*pcx, pcxbuf;
	byte	palette[768];
	byte	*pix;
	int	x, y;
	int	dataByte, runLength;
	int	count;

//
// parse the PCX file
//
	fread (&pcxbuf, 1, sizeof(pcxbuf), f);

	pcx = &pcxbuf;

	if (pcx->manufacturer != 0x0a
		|| pcx->version != 5
		|| pcx->encoding != 1
		|| pcx->bits_per_pixel != 8
		|| pcx->xmax >= 320
		|| pcx->ymax >= 256)
		Sys_Error ("LoadPCX: Bad pcx file");

	// seek to palette
	fseek (f, -768, SEEK_END);
	fread (palette, 1, 768, f);

	fseek (f, sizeof(pcxbuf) - 4, SEEK_SET);

	count = (pcx->xmax+1) * (pcx->ymax+1);
	pcx_rgb = malloc( count * 4);

	for (y=0 ; y<=pcx->ymax ; y++)
	{
		pix = pcx_rgb + 4*y*(pcx->xmax+1);
		for (x=0 ; x<=pcx->ymax ; )
		{
			dataByte = fgetc(f);

			if((dataByte & 0xC0) == 0xC0)
			{
				runLength = dataByte & 0x3F;
				dataByte = fgetc(f);
			}
			else
				runLength = 1;

			while(runLength-- > 0)
			{
				pix[0] = palette[dataByte*3];
				pix[1] = palette[dataByte*3+1];
				pix[2] = palette[dataByte*3+2];
				pix[3] = 255;
				pix += 4;
				x++;
			}
		}
	}

	sky_width = (int)(pcx->xmax) + 1;
	sky_height = (int)(pcx->ymax) + 1;
}

/*
=========================================================

TARGA LOADING

=========================================================
*/

typedef struct _TargaHeader {
	unsigned char 	id_length, colormap_type, image_type;
	unsigned short	colormap_index, colormap_length;
	unsigned char	colormap_size;
	unsigned short	x_origin, y_origin, width, height;
	unsigned char	pixel_size, attributes;
} TargaHeader;


static TargaHeader targa_header;
byte		   *targa_rgba;

static int fgetLittleShort (FILE *f)
{
	byte	b1, b2;

	b1 = fgetc(f);
	b2 = fgetc(f);

	return (short)(b1 + b2*256);
}

static int fgetLittleLong (FILE *f)
{
	byte	b1, b2, b3, b4;

	b1 = fgetc(f);
	b2 = fgetc(f);
	b3 = fgetc(f);
	b4 = fgetc(f);

	return b1 + (b2<<8) + (b3<<16) + (b4<<24);
}


/*
=============
LoadTGA
=============
*/
void LoadTGA (FILE *fin)
{
	int	columns, rows, numPixels;
	byte	*pixbuf;
	int	row, column;

	targa_header.id_length = fgetc(fin);
	targa_header.colormap_type = fgetc(fin);
	targa_header.image_type = fgetc(fin);

	targa_header.colormap_index = fgetLittleShort(fin);
	targa_header.colormap_length = fgetLittleShort(fin);
	targa_header.colormap_size = fgetc(fin);
	targa_header.x_origin = fgetLittleShort(fin);
	targa_header.y_origin = fgetLittleShort(fin);
	targa_header.width = fgetLittleShort(fin);
	targa_header.height = fgetLittleShort(fin);
	targa_header.pixel_size = fgetc(fin);
	targa_header.attributes = fgetc(fin);

	if (targa_header.image_type!=2
		&& targa_header.image_type!=10)
		Sys_Error ("LoadTGA: Only type 2 and 10 targa RGB images supported");

	if (targa_header.colormap_type !=0
		|| (targa_header.pixel_size!=32 && targa_header.pixel_size!=24))
		Sys_Error ("Texture_LoadTGA: Only 32 or 24 bit images supported (no colormaps)");

	columns = targa_header.width;
	rows = targa_header.height;
	numPixels = columns * rows;

	targa_rgba = malloc (numPixels*4);

	if (targa_header.id_length != 0)
		fseek(fin, targa_header.id_length, SEEK_CUR);  // skip TARGA image comment

	if (targa_header.image_type==2) {  // Uncompressed, RGB images
		for(row=rows-1; row>=0; row--) {
			pixbuf = targa_rgba + row*columns*4;
			for(column=0; column<columns; column++) {
				unsigned char red,green,blue,alphabyte;
				switch (targa_header.pixel_size) {
					case 24:

							blue = getc(fin);
							green = getc(fin);
							red = getc(fin);
							*pixbuf++ = red;
							*pixbuf++ = green;
							*pixbuf++ = blue;
							*pixbuf++ = 255;
							break;
					case 32:
							blue = getc(fin);
							green = getc(fin);
							red = getc(fin);
							alphabyte = getc(fin);
							*pixbuf++ = red;
							*pixbuf++ = green;
							*pixbuf++ = blue;
							*pixbuf++ = alphabyte;
							break;
				}
			}
		}
	}
	else if (targa_header.image_type==10) {   // Runlength encoded RGB images
		unsigned char red,green,blue,alphabyte,packetHeader,packetSize,j;
		for(row=rows-1; row>=0; row--) {
			pixbuf = targa_rgba + row*columns*4;
			for(column=0; column<columns; ) {
				packetHeader=getc(fin);
				packetSize = 1 + (packetHeader & 0x7f);
				if (packetHeader & 0x80) {        // run-length packet
					switch (targa_header.pixel_size) {
						case 24:
								blue = getc(fin);
								green = getc(fin);
								red = getc(fin);
								alphabyte = 255;
								break;
						case 32:
								blue = getc(fin);
								green = getc(fin);
								red = getc(fin);
								alphabyte = getc(fin);
								break;
					}

					for(j=0;j<packetSize;j++) {
						*pixbuf++=red;
						*pixbuf++=green;
						*pixbuf++=blue;
						*pixbuf++=alphabyte;
						column++;
						if (column==columns) { // run spans across rows
							column=0;
							if (row>0)
								row--;
							else
								goto breakOut;
							pixbuf = targa_rgba + row*columns*4;
						}
					}
				}
				else {                            // non run-length packet
					for(j=0;j<packetSize;j++) {
						switch (targa_header.pixel_size) {
							case 24:
									blue = getc(fin);
									green = getc(fin);
									red = getc(fin);
									*pixbuf++ = red;
									*pixbuf++ = green;
									*pixbuf++ = blue;
									*pixbuf++ = 255;
									break;
							case 32:
									blue = getc(fin);
									green = getc(fin);
									red = getc(fin);
									alphabyte = getc(fin);
									*pixbuf++ = red;
									*pixbuf++ = green;
									*pixbuf++ = blue;
									*pixbuf++ = alphabyte;
									break;
						}
						column++;
						if (column==columns) { // pixel packet run spans across rows
							column=0;
							if (row>0)
								row--;
							else
								goto breakOut;
							pixbuf = targa_rgba + row*columns*4;
						}
					}
				}
			}
			breakOut:;
		}
	}

	fclose(fin);

	sky_width = targa_header.width;
	sky_height = targa_header.height;
}

/*
==================
RotateImage
==================
*/
static void RotateImage (int *Img, int width, int height, qboolean Left)
{
	int i, j, Size, *Rot;

	if (width != height)
	{
		Con_Printf ("RotateImage: image not symmetrical (%dx%d)\n", width, height);
		return;
	}
	
	Size = width * height * sizeof(int);

	if (!(Rot = malloc (Size)))
	{
		Con_Printf ("RotateImage: not enough memory for %dk\n", Size / 1024);
		return;
	}
	
	for (i = 0; i < height; ++i)
	{
		for (j = 0; j < width; ++j)
		{
			if (Left)
				Rot[(height - 1 - j) * width + i] = Img[i * width + j];
			else
				Rot[j * width + (width - 1 - i)] = Img[i * width + j];
		}
	}

	memcpy (Img, Rot, Size);
	
	free (Rot);
}

/*
==================
R_LoadSkys
==================
*/
static char *suf[6] = {"rt", "bk", "lf", "ft", "up", "dn"};
static int  suf_ord1[6] = {0, 1, 2, 3, 4, 5}; // Q2/VRML order
static int  suf_ord2[6] = {3, 0, 1, 2, 4, 5}; // Rotated 90 degrees left
static char skybox_name[MAX_QPATH] = "";      // name of current skybox

void R_LoadSkys (char *skybox)
{
	int		i, j, *suf_ord;
	FILE		*f;
	char		name[MAX_QPATH];
	byte		*data[6];
	qboolean	RotateSkyBox = false;
	static qboolean OldRotated = false;

	if (cl.worldmodel->name != NULL)
	{
		name[0] = '\0';
	
		COM_StripExtension (cl.worldmodel->name + 5, name);

		if (!stricmp(name, "invein"))
			RotateSkyBox = true; // Invein's skybox is invalidly rotated 90 degrees right
	}

	if (RotateSkyBox == OldRotated && !strcmp(skybox, skybox_name)) //no change
	{
		Cvar_SetValue ("r_oldsky", skybox_name[0] == 0);
		return;
	}

	OldRotated = RotateSkyBox;

	// Make sure horizontal images are rotated correctly
	suf_ord = RotateSkyBox ? suf_ord2 : suf_ord1;

	for (i=0 ; i<6 ; i++)
	{
                for (j = 0; j < 2; ++j)
		{
			sprintf (name, "gfx/env/%s%s.%s", skybox, suf[suf_ord[i]], j == 0 ? "tga" : "pcx");
			COM_FOpenFile (name, &f);
			if (!f)
				continue;

			if (j == 0)
			{
				LoadTGA (f);
				data[i] = targa_rgba;
			}
			else
			{
				LoadPCX (f);
				data[i] = pcx_rgb;
			}
			
			// If entire skybox is rotated, up/down images must be rotated right/left
			if (i >= 4 && RotateSkyBox)
				RotateImage ((int *)data[i], sky_width, sky_height, i == 5);

			break;
		}

		if (j == 2)
		{
			Con_Printf ("Couldn't load %s\n", name);
			break;
		}
	}

	if (i == 6)
	{
		for (j = 0; j < 6; ++j)
		{
			GL_Bind (skyboxtextures + j);
			sprintf (name, "gfx/env/%s%s", skybox, suf[suf_ord[j]]);
			GL_Upload32 (data[j], sky_width, sky_height, false, false, name);
		}
	}

	for (j = 0; j < i; ++j)
		free (data[j]);

	if (i == 6)
	{
		strcpy (skybox_name, skybox);
		Con_DPrintf ("skybox set to %s%s\n", skybox, RotateSkyBox ? " and rotated" : "");
	}

	// Enable/disable skybox
	Cvar_SetValue ("r_oldsky", skybox_name[0] == 0);
}

/*
=================
R_Sky_NewMap
=================
*/
void R_Sky_NewMap (void)
{
	char	key[MAX_KEY], value[MAX_VALUE];
	char	*data;

	// initially no skybox
	Cvar_SetValue ("r_oldsky", 1);

	data = cl.worldmodel->entities;
	if (!data)
		return;

	data = COM_Parse(data);
	if (!data) //should never happen
		return; // error
	if (com_token[0] != '{') //should never happen
		return; // error
	while (1)
	{
		data = COM_Parse(data);
		if (!data)
			return; // error
		if (com_token[0] == '}')
			break; // end of worldspawn
		if (com_token[0] == '_')
			strcpy(key, com_token + 1);
		else
			strcpy(key, com_token);
		while (key[strlen(key)-1] == ' ') // remove trailing spaces
			key[strlen(key)-1] = 0;
		data = COM_Parse(data);
		if (!data)
			return; // error
		strcpy(value, com_token);

		if (!strcmp("sky", key) && value[0])
			R_LoadSkys (value);
	}
}

/*
=================
R_SkyCommand_f
=================
*/
void R_SkyCommand_f (void)
{
	switch (Cmd_Argc())
	{
	case 1:
		Con_Printf("\"sky\" is \"%s\"\n", skybox_name);
		break;
	case 2:
		R_LoadSkys (Cmd_Argv(1));
		break;
	default:
		Con_Printf("usage: [load]sky <skyname>\n");
	}
}

static vec3_t skyclip[6] = {
	{1,1,0},
	{1,-1,0},
	{0,-1,1},
	{0,1,1},
	{1,0,1},
	{-1,0,1}
};

// 1 = s, 2 = t, 3 = 2048
static int st_to_vec[6][3] =
{
	{3,-1,2},
	{-3,1,2},

	{1,3,2},
	{-1,-3,2},

	{-2,-1,3},		// 0 degrees yaw, look straight up
	{2,-1,-3}		// look straight down

//	{-1,2,3},
//	{1,2,-3}
};

// s = [0]/[2], t = [1]/[2]
static int vec_to_st[6][3] =
{
	{-2,3,1},
	{2,3,-1},

	{1,3,2},
	{-1,3,-2},

	{-2,-1,3},
	{-2,1,-3}

//	{-1,2,3},
//	{1,2,-3}
};

static float skymins[2][6], skymaxs[2][6];

static void DrawSkyPolygon (int nump, vec3_t vecs)
{
	int	i,j;
	vec3_t	v, av;
	float	s, t, dv;
	int	axis;
	float	*vp;

	// decide which face it maps to
	VectorCopy (vec3_origin, v);
	for (i=0, vp=vecs ; i<nump ; i++, vp+=3)
	{
		VectorAdd (vp, v, v);
	}
	av[0] = fabs(v[0]);
	av[1] = fabs(v[1]);
	av[2] = fabs(v[2]);
	if (av[0] > av[1] && av[0] > av[2])
	{
		if (v[0] < 0)
			axis = 1;
		else
			axis = 0;
	}
	else if (av[1] > av[2] && av[1] > av[0])
	{
		if (v[1] < 0)
			axis = 3;
		else
			axis = 2;
	}
	else
	{
		if (v[2] < 0)
			axis = 5;
		else
			axis = 4;
	}

	// project new texture coords
	for (i=0 ; i<nump ; i++, vecs+=3)
	{
		j = vec_to_st[axis][2];
		if (j > 0)
			dv = vecs[j - 1];
		else
			dv = -vecs[-j - 1];

		j = vec_to_st[axis][0];
		if (j < 0)
			s = -vecs[-j -1] / dv;
		else
			s = vecs[j-1] / dv;
		j = vec_to_st[axis][1];
		if (j < 0)
			t = -vecs[-j -1] / dv;
		else
			t = vecs[j-1] / dv;

		if (s < skymins[0][axis])
			skymins[0][axis] = s;
		if (t < skymins[1][axis])
			skymins[1][axis] = t;
		if (s > skymaxs[0][axis])
			skymaxs[0][axis] = s;
		if (t > skymaxs[1][axis])
			skymaxs[1][axis] = t;
	}
}

#define	MAX_CLIP_VERTS	64
static void ClipSkyPolygon (int nump, vec3_t vecs, int stage)
{
	float		*norm;
	float		*v;
	qboolean	front, back;
	float		d, e;
	float		dists[MAX_CLIP_VERTS];
	int		sides[MAX_CLIP_VERTS];
	vec3_t		newv[2][MAX_CLIP_VERTS];
	int		newc[2];
	int		i, j;

	if (nump > MAX_CLIP_VERTS-2)
		Sys_Error ("ClipSkyPolygon: MAX_CLIP_VERTS");
	if (stage == 6)
	{	// fully clipped, so draw it
		DrawSkyPolygon (nump, vecs);
		return;
	}

	front = back = false;
	norm = skyclip[stage];
	for (i=0, v = vecs ; i<nump ; i++, v+=3)
	{
		d = DotProduct (v, norm);
		if (d > ON_EPSILON)
		{
			front = true;
			sides[i] = SIDE_FRONT;
		}
		else if (d < ON_EPSILON)
		{
			back = true;
			sides[i] = SIDE_BACK;
		}
		else
			sides[i] = SIDE_ON;
		dists[i] = d;
	}

	if (!front || !back)
	{	// not clipped
		ClipSkyPolygon (nump, vecs, stage+1);
		return;
	}

	// clip it
	sides[i] = sides[0];
	dists[i] = dists[0];
	VectorCopy (vecs, (vecs+(i*3)) );
	newc[0] = newc[1] = 0;

	for (i=0, v = vecs ; i<nump ; i++, v+=3)
	{
		switch (sides[i])
		{
		case SIDE_FRONT:
			VectorCopy (v, newv[0][newc[0]]);
			newc[0]++;
			break;
		case SIDE_BACK:
			VectorCopy (v, newv[1][newc[1]]);
			newc[1]++;
			break;
		case SIDE_ON:
			VectorCopy (v, newv[0][newc[0]]);
			newc[0]++;
			VectorCopy (v, newv[1][newc[1]]);
			newc[1]++;
			break;
		}

		if (sides[i] == SIDE_ON || sides[i+1] == SIDE_ON || sides[i+1] == sides[i])
			continue;

		d = dists[i] / (dists[i] - dists[i+1]);
		for (j=0 ; j<3 ; j++)
		{
			e = v[j] + d*(v[j+3] - v[j]);
			newv[0][newc[0]][j] = e;
			newv[1][newc[1]][j] = e;
		}
		newc[0]++;
		newc[1]++;
	}

	// continue
	ClipSkyPolygon (newc[0], newv[0][0], stage+1);
	ClipSkyPolygon (newc[1], newv[1][0], stage+1);
}

/*
=================
R_DrawSkyChain
=================
*/
void R_DrawSkyChain (msurface_t *s)
{
 	if (r_oldsky.value)
	{
		msurface_t  *fa;
//		int	    i;

		GL_DisableMultitexture();

		// used when gl_texsort is on
		GL_Bind(solidskytexture);
		speedscale = realtime*8;
		speedscale -= (int)speedscale & ~127 ;

		for (fa=s ; fa ; fa=fa->texturechain)
			EmitSkyPolys (fa);
/*		for (fa=s, i=0 ; fa ; fa=fa->texturechain, ++i)
		{
			if (i == 1000)
				Sys_Error ("EmitSkyPolys runaway loop 1000");

			if (i > 0 && fa == s)
				Sys_Error ("EmitSkyPolys runaway loop fa==s");

			EmitSkyPolys (fa);
		}*/

		glEnable (GL_BLEND);
		GL_Bind (alphaskytexture);
		speedscale = realtime*16;
		speedscale -= (int)speedscale & ~127 ;

		for (fa=s ; fa ; fa=fa->texturechain)
			EmitSkyPolys (fa);

		glDisable (GL_BLEND);
  	}
  	else
  	{
		msurface_t  *fa;
		int	    i;
		vec3_t	    verts[MAX_CLIP_VERTS], origin;
		glpoly_t    *p;

		// calculate vertex values for sky box

		VectorCopy (r_origin, origin);
		origin[0] += 0.001; // Offset slightly horizontally to avoid initial top side distortion, kludge

		for (fa=s ; fa ; fa=fa->texturechain)
		{
			for (p=fa->polys ; p ; p=p->next)
			{
				for (i=0 ; i<p->numverts ; i++)
					VectorSubtract (p->verts[i], origin, verts[i]);

				ClipSkyPolygon (p->numverts, verts[0], 0);
			}
		}
	}
}


/*
==============
R_ClearSkyBox
==============
*/
void R_ClearSkyBox (void)
{
	int i;

	if (r_oldsky.value)
		return;

	for (i=0 ; i<6 ; i++)
	{
		skymins[0][i] = skymins[1][i] = 9999;
		skymaxs[0][i] = skymaxs[1][i] = -9999;
	}
}

static void MakeSkyVec (float s, float t, int axis)
{
	vec3_t	v, b;
	int	j, k, farclip;
	float	w, h;

	// Compromise; big enough to avoid sky covering world for the Nehahra maps,
	// but small enough to avoid hiding skyboxes in fog
	farclip = gl_fogenable.value && !gl_fogdisable.value ? gl_skyclip.value : GL_FARCLIP;

	if (farclip > GL_FARCLIP)
		farclip = GL_FARCLIP;

	b[0] = s * farclip / 2;
	b[1] = t * farclip / 2;
	b[2] = farclip / 2;

	for (j=0 ; j<3 ; j++)
	{
		k = st_to_vec[axis][j];
		if (k < 0)
			v[j] = -b[-k - 1];
		else
			v[j] = b[k - 1];
		v[j] += r_origin[j];
	}

	// avoid bilerp seam
	s = (s+1)*0.5;
	t = (t+1)*0.5;

	w = sky_width;
	h = sky_height;
	s = s * (w-1)/w + 0.5/w;
	t = t * (h-1)/h + 0.5/h;

	t = 1.0 - t;
	glTexCoord2f (s, t);
	glVertex3fv (v);
}

/*
==============
R_DrawSkyBox
==============
*/
static int skytexorder[6] = {0,2,1,3,4,5};

void R_DrawSkyBox (void)
{
	int	   i, j, k;
	vec3_t	   v;
	float	   s, t;
	msurface_t *fa;

	if (r_oldsky.value)
		return;

	if (gl_do_skyfix)
	{
		// Non-transparent skybox only works in multitexture for now
		if (!skychain)
			return;

		R_ClearSkyBox ();
		R_DrawSkyChain (skychain);

		GL_DisableMultitexture ();
	}

	for (i=0 ; i<6 ; i++)
	{
		if (skymins[0][i] >= skymaxs[0][i]
		|| skymins[1][i] >= skymaxs[1][i])
			continue;

		GL_Bind (skyboxtextures + skytexorder[i]);
		glBegin (GL_QUADS);
		MakeSkyVec (skymins[0][i], skymins[1][i], i);
		MakeSkyVec (skymins[0][i], skymaxs[1][i], i);
		MakeSkyVec (skymaxs[0][i], skymaxs[1][i], i);
		MakeSkyVec (skymaxs[0][i], skymins[1][i], i);
		glEnd ();
	}

	if (!gl_do_skyfix)
		return;

	// Non-transparent skybox only works in multitexture for now
	glDisable (GL_TEXTURE_2D);
	glColorMask (GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
	glEnable (GL_BLEND);
	glBlendFunc (GL_ZERO, GL_ONE);

	for (fa = skychain ; fa ; fa = fa->texturechain)
		EmitFlatPoly (fa);

	glEnable (GL_TEXTURE_2D);
	glColorMask (GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
	glDisable (GL_BLEND);
	glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	skychain = NULL;
}

//===============================================================

/*
=============
R_InitSky

A sky texture is 256*128, with the right side being a masked overlay
==============
*/
void R_InitSky (texture_t *mt)
{
	int			i, j, p;
	byte		*src;
	unsigned	trans[128*128];
	unsigned	transpix;
	int			r, g, b;
	unsigned	*rgba;

	src = (byte *)mt + mt->offsets[0];

	// make an average value for the back to avoid
	// a fringe on the top level

	r = g = b = 0;
	for (i=0 ; i<128 ; i++)
		for (j=0 ; j<128 ; j++)
		{
			p = src[i*256 + j + 128];
			rgba = &d_8to24table[p];
			trans[(i*128) + j] = *rgba;
			r += ((byte *)rgba)[0];
			g += ((byte *)rgba)[1];
			b += ((byte *)rgba)[2];
		}

	((byte *)&transpix)[0] = r/(128*128);
	((byte *)&transpix)[1] = g/(128*128);
	((byte *)&transpix)[2] = b/(128*128);
	((byte *)&transpix)[3] = 0;


	if (!solidskytexture)
		solidskytexture = texture_extension_number++;
	GL_Bind (solidskytexture );
	glTexImage2D (GL_TEXTURE_2D, 0, gl_solid_format, 128, 128, 0, GL_RGBA, GL_UNSIGNED_BYTE, trans);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


	for (i=0 ; i<128 ; i++)
		for (j=0 ; j<128 ; j++)
		{
			p = src[i*256 + j];
			if (p == 0)
				trans[(i*128) + j] = transpix;
			else
				trans[(i*128) + j] = d_8to24table[p];
		}

	if (!alphaskytexture)
		alphaskytexture = texture_extension_number++;
	GL_Bind(alphaskytexture);
	glTexImage2D (GL_TEXTURE_2D, 0, gl_alpha_format, 128, 128, 0, GL_RGBA, GL_UNSIGNED_BYTE, trans);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
}