/*
Copyright (C) 1996-2001 Id Software, Inc.
Copyright (C) 2002-2009 John Fitzgibbons and others
Copyright (C) 2007-2008 Kristian Duske
Copyright (C) 2010-2014 QuakeSpasm developers

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_sky.c

#include "q_defs.h"

#define MAX_CLIP_VERTS 64

float Fog_GetDensity(void);
float *Fog_GetColor(void);

extern  qmodel_t        *loadmodel;
extern  int32_t rs_skypolys; //for r_speeds readout
extern  int32_t rs_skypasses; //for r_speeds readout
float   skyflatcolor[3];
float   skymins[2][6], skymaxs[2][6];

char    skybox_name[32] = ""; //name of current skybox, or "" if no skybox

gltexture_t     *skybox_textures[6];
gltexture_t     *solidskytexture, *alphaskytexture;

extern cvar_t gl_farclip;
cvar_t r_fastsky = {"r_fastsky", "0", CVAR_NONE};
cvar_t r_sky_quality = {"r_sky_quality", "12", CVAR_NONE};
cvar_t r_skyalpha = {"r_skyalpha", "1", CVAR_NONE};
cvar_t r_skyfog = {"r_skyfog", "0.5", CVAR_NONE};

int32_t         skytexorder[6] = {0, 2, 1, 3, 4, 5}; //for skybox

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

int32_t st_to_vec[6][3] =
{
	{3, -1, 2},
	{-3, 1, 2},
	{1, 3, 2},
	{-1, -3, 2},
	{-2, -1, 3},            // straight up
	{2, -1, -3}             // straight down
};

int32_t vec_to_st[6][3] =
{
	{-2, 3, 1},
	{2, 3, -1},
	{1, 3, 2},
	{-1, 3, -2},
	{-2, -1, 3},
	{-2, 1, -3}
};

float   skyfog; // ericw

//==============================================================================
//
//  INIT
//
//==============================================================================

/*
=============
Sky_LoadTexture

A sky texture is 256*128, with the left side being a masked overlay
==============
*/
void Sky_LoadTexture(texture_t *mt)
{
	char            texturename[64];
	int32_t                 i, j, p, r, g, b, count;
	byte            *src;
	static byte     front_data[128 * 128]; //FIXME: Hunk_Alloc
	static byte     back_data[128 * 128]; //FIXME: Hunk_Alloc
	unsigned        *rgba;

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

// extract back layer and upload
	for(i = 0 ; i < 128 ; i++)
		for(j = 0 ; j < 128 ; j++)
			back_data[(i * 128) + j] = src[i * 256 + j + 128];

	q_snprintf(texturename, sizeof(texturename), "%s:%s_back", loadmodel->name, mt->name);
	solidskytexture = TexMgr_LoadImage(loadmodel, texturename, 128, 128, SRC_INDEXED, back_data, "", (src_offset_t)back_data, TEXPREF_NONE);

// extract front layer and upload
	for(i = 0 ; i < 128 ; i++)
		for(j = 0 ; j < 128 ; j++)
		{
			front_data[(i * 128) + j] = src[i * 256 + j];
			if(front_data[(i * 128) + j] == 0)
				front_data[(i * 128) + j] = 255;
		}

	q_snprintf(texturename, sizeof(texturename), "%s:%s_front", loadmodel->name, mt->name);
	alphaskytexture = TexMgr_LoadImage(loadmodel, texturename, 128, 128, SRC_INDEXED, front_data, "", (src_offset_t)front_data, TEXPREF_ALPHA);

// calculate r_fastsky color based on average of all opaque foreground colors
	r = g = b = count = 0;
	for(i = 0 ; i < 128 ; i++)
		for(j = 0 ; j < 128 ; j++)
		{
			p = src[i * 256 + j];
			if(p != 0)
			{
				rgba = &d_8to24table[p];
				r += ((byte *)rgba)[0];
				g += ((byte *)rgba)[1];
				b += ((byte *)rgba)[2];
				count++;
			}
		}
	skyflatcolor[0] = (float)r / (count * 255);
	skyflatcolor[1] = (float)g / (count * 255);
	skyflatcolor[2] = (float)b / (count * 255);
}

/*
==================
Sky_LoadSkyBox
==================
*/
const char      *suf[6] = {"rt", "bk", "lf", "ft", "up", "dn"};
void Sky_LoadSkyBox(const char *name)
{
	int32_t         i, mark, width, height;
	char    filename[MAX_OSPATH];
	byte    *data;
	bool nonefound = true;

	if(strcmp(skybox_name, name) == 0)
		return; //no change

	//purge old textures
	for(i = 0; i < 6; i++)
	{
		if(skybox_textures[i] && skybox_textures[i] != notexture)
			TexMgr_FreeTexture(skybox_textures[i]);
		skybox_textures[i] = NULL;
	}

	//turn off skybox if sky is set to ""
	if(name[0] == 0)
	{
		skybox_name[0] = 0;
		return;
	}

	//load textures
	for(i = 0; i < 6; i++)
	{
		mark = Hunk_LowMark();
		q_snprintf(filename, sizeof(filename), "gfx/env/%s%s", name, suf[i]);
		data = Image_LoadImage(filename, &width, &height);
		if(data)
		{
			skybox_textures[i] = TexMgr_LoadImage(cl.worldmodel, filename, width, height, SRC_RGBA, data, filename, 0, TEXPREF_NONE);
			nonefound = false;
		}
		else
		{
			Con_Printf("Couldn't load %s\n", filename);
			skybox_textures[i] = notexture;
		}
		Hunk_FreeToLowMark(mark);
	}

	if(nonefound)  // go back to scrolling sky if skybox is totally missing
	{
		for(i = 0; i < 6; i++)
		{
			if(skybox_textures[i] && skybox_textures[i] != notexture)
				TexMgr_FreeTexture(skybox_textures[i]);
			skybox_textures[i] = NULL;
		}
		skybox_name[0] = 0;
		return;
	}

	strcpy(skybox_name, name);
}

/*
=================
Sky_NewMap
=================
*/
void Sky_NewMap(void)
{
	char    key[128], value[4096];
	const char      *data;
	int32_t         i;

	//
	// initially no sky
	//
	skybox_name[0] = 0;
	for(i = 0; i < 6; i++)
		skybox_textures[i] = NULL;
	skyfog = r_skyfog.value;

	//
	// read worldspawn (this is so ugly, and shouldn't it be done on the server?)
	//
	data = cl.worldmodel->entities;
	if(!data)
		return; //FIXME: how could this possibly ever happen? -- if there's no
	// worldspawn then the sever wouldn't send the loadmap message to the client

	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))
			Sky_LoadSkyBox(value);

		if(!strcmp("skyfog", key))
			skyfog = atof(value);

#if 1 //also accept non-standard keys
		else if(!strcmp("skyname", key))  //half-life
			Sky_LoadSkyBox(value);
		else if(!strcmp("qlsky", key))  //quake lives
			Sky_LoadSkyBox(value);
#endif
	}
}

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

/*
====================
R_SetSkyfog_f -- ericw
====================
*/
static void R_SetSkyfog_f(cvar_t *var)
{
// clear any skyfog setting from worldspawn
	skyfog = var->value;
}

/*
=============
Sky_Init
=============
*/
void Sky_Init(void)
{
	int32_t         i;

	Cvar_RegisterVariable(&r_fastsky);
	Cvar_RegisterVariable(&r_sky_quality);
	Cvar_RegisterVariable(&r_skyalpha);
	Cvar_RegisterVariable(&r_skyfog);
	Cvar_SetCallback(&r_skyfog, R_SetSkyfog_f);

	Cmd_AddCommand("sky", Sky_SkyCommand_f);

	for(i = 0; i < 6; i++)
		skybox_textures[i] = NULL;
}

//==============================================================================
//
//  PROCESS SKY SURFS
//
//==============================================================================

/*
=================
Sky_ProjectPoly

update sky bounds
=================
*/
void Sky_ProjectPoly(int32_t nump, vec3_t vecs)
{
	int32_t         i, j;
	vec3_t  v, av;
	float   s, t, dv;
	int32_t         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;
	}
}

/*
=================
Sky_ClipPoly
=================
*/
void Sky_ClipPoly(int32_t nump, vec3_t vecs, int32_t stage)
{
	float   *norm;
	float   *v;
	bool    front, back;
	float   d, e;
	float   dists[MAX_CLIP_VERTS];
	int32_t         sides[MAX_CLIP_VERTS];
	vec3_t  newv[2][MAX_CLIP_VERTS];
	int32_t         newc[2];
	int32_t         i, j;

	if(nump > MAX_CLIP_VERTS - 2)
		Sys_Error("Sky_ClipPoly: MAX_CLIP_VERTS");
	if(stage == 6)  // fully clipped
	{
		Sky_ProjectPoly(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
		Sky_ClipPoly(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
	Sky_ClipPoly(newc[0], newv[0][0], stage + 1);
	Sky_ClipPoly(newc[1], newv[1][0], stage + 1);
}

/*
================
Sky_ProcessPoly
================
*/
void Sky_ProcessPoly(glpoly_t  *p)
{
	int32_t                 i;
	vec3_t          verts[MAX_CLIP_VERTS];

	//draw it
	DrawGLPoly(p);
	rs_brushpasses++;

	//update sky bounds
	if(!r_fastsky.value)
	{
		for(i = 0 ; i < p->numverts ; i++)
			VectorSubtract(p->verts[i], r_origin, verts[i]);
		Sky_ClipPoly(p->numverts, verts[0], 0);
	}
}

/*
================
Sky_ProcessTextureChains -- handles sky polys in world model
================
*/
void Sky_ProcessTextureChains(void)
{
	int32_t                 i;
	msurface_t      *s;
	texture_t       *t;

	if(!r_drawworld_cheatsafe)
		return;

	for(i = 0 ; i < cl.worldmodel->numtextures ; i++)
	{
		t = cl.worldmodel->textures[i];

		if(!t || !t->texturechains[chain_world] || !(t->texturechains[chain_world]->flags & SURF_DRAWSKY))
			continue;

		for(s = t->texturechains[chain_world]; s; s = s->texturechain)
			if(!s->culled)
				Sky_ProcessPoly(s->polys);
	}
}

/*
================
Sky_ProcessEntities -- handles sky polys on brush models
================
*/
void Sky_ProcessEntities(void)
{
	entity_t        *e;
	msurface_t      *s;
	glpoly_t        *p;
	int32_t                 i, j, k, mark;
	float           dot;
	bool    rotated;
	vec3_t          temp, forward, right, up;

	if(!r_drawentities.value)
		return;

	for(i = 0 ; i < cl_numvisedicts ; i++)
	{
		e = cl_visedicts[i];

		if(e->model->type != mod_brush)
			continue;

		if(R_CullModelForEntity(e))
			continue;

		if(e->alpha == ENTALPHA_ZERO)
			continue;

		VectorSubtract(r_refdef.vieworg, e->origin, modelorg);
		if(e->angles[0] || e->angles[1] || e->angles[2])
		{
			rotated = true;
			AngleVectors(e->angles, forward, right, up);
			VectorCopy(modelorg, temp);
			modelorg[0] = DotProduct(temp, forward);
			modelorg[1] = -DotProduct(temp, right);
			modelorg[2] = DotProduct(temp, up);
		}
		else
			rotated = false;

		s = &e->model->surfaces[e->model->firstmodelsurface];

		for(j = 0 ; j < e->model->nummodelsurfaces ; j++, s++)
		{
			if(s->flags & SURF_DRAWSKY)
			{
				dot = DotProduct(modelorg, s->plane->normal) - s->plane->dist;
				if(((s->flags & SURF_PLANEBACK) && (dot < -BACKFACE_EPSILON)) ||
				                (!(s->flags & SURF_PLANEBACK) && (dot > BACKFACE_EPSILON)))
				{
					//copy the polygon and translate manually, since Sky_ProcessPoly needs it to be in world space
					mark = Hunk_LowMark();
					p = (glpoly_t *) Hunk_Alloc(sizeof(*s->polys));  //FIXME: don't allocate for each poly
					p->numverts = s->polys->numverts;
					for(k = 0; k < p->numverts; k++)
					{
						if(rotated)
						{
							p->verts[k][0] = e->origin[0] + s->polys->verts[k][0] * forward[0]
							                 - s->polys->verts[k][1] * right[0]
							                 + s->polys->verts[k][2] * up[0];
							p->verts[k][1] = e->origin[1] + s->polys->verts[k][0] * forward[1]
							                 - s->polys->verts[k][1] * right[1]
							                 + s->polys->verts[k][2] * up[1];
							p->verts[k][2] = e->origin[2] + s->polys->verts[k][0] * forward[2]
							                 - s->polys->verts[k][1] * right[2]
							                 + s->polys->verts[k][2] * up[2];
						}
						else
							VectorAdd(s->polys->verts[k], e->origin, p->verts[k]);
					}
					Sky_ProcessPoly(p);
					Hunk_FreeToLowMark(mark);
				}
			}
		}
	}
}

//==============================================================================
//
//  RENDER SKYBOX
//
//==============================================================================

/*
==============
Sky_EmitSkyBoxVertex
==============
*/
void Sky_EmitSkyBoxVertex(float s, float t, int32_t axis)
{
	vec3_t          v, b;
	int32_t                 j, k;
	float           w, h;

	b[0] = s * gl_farclip.value / sqrt(3.0);
	b[1] = t * gl_farclip.value / sqrt(3.0);
	b[2] = gl_farclip.value / sqrt(3.0);

	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];
	}

	// convert from range [-1,1] to [0,1]
	s = (s + 1) * 0.5;
	t = (t + 1) * 0.5;

	// avoid bilerp seam
	w = skybox_textures[skytexorder[axis]]->width;
	h = skybox_textures[skytexorder[axis]]->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);
}

/*
==============
Sky_DrawSkyBox

FIXME: eliminate cracks by adding an extra vert on tjuncs
==============
*/
void Sky_DrawSkyBox(void)
{
	int32_t         i;

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

		GL_Bind(skybox_textures[skytexorder[i]]);

#if 1 //FIXME: this is to avoid tjunctions until i can do it the right way
		skymins[0][i] = -1;
		skymins[1][i] = -1;
		skymaxs[0][i] = 1;
		skymaxs[1][i] = 1;
#endif
		glBegin(GL_QUADS);
		Sky_EmitSkyBoxVertex(skymins[0][i], skymins[1][i], i);
		Sky_EmitSkyBoxVertex(skymins[0][i], skymaxs[1][i], i);
		Sky_EmitSkyBoxVertex(skymaxs[0][i], skymaxs[1][i], i);
		Sky_EmitSkyBoxVertex(skymaxs[0][i], skymins[1][i], i);
		glEnd();

		rs_skypolys++;
		rs_skypasses++;

		if(Fog_GetDensity() > 0 && skyfog > 0)
		{
			float *c;

			c = Fog_GetColor();
			glEnable(GL_BLEND);
			glDisable(GL_TEXTURE_2D);
			glColor4f(c[0], c[1], c[2], CLAMP(0.0, skyfog, 1.0));

			glBegin(GL_QUADS);
			Sky_EmitSkyBoxVertex(skymins[0][i], skymins[1][i], i);
			Sky_EmitSkyBoxVertex(skymins[0][i], skymaxs[1][i], i);
			Sky_EmitSkyBoxVertex(skymaxs[0][i], skymaxs[1][i], i);
			Sky_EmitSkyBoxVertex(skymaxs[0][i], skymins[1][i], i);
			glEnd();

			glColor3f(1, 1, 1);
			glEnable(GL_TEXTURE_2D);
			glDisable(GL_BLEND);

			rs_skypasses++;
		}
	}
}

//==============================================================================
//
//  RENDER CLOUDS
//
//==============================================================================

/*
==============
Sky_SetBoxVert
==============
*/
void Sky_SetBoxVert(float s, float t, int32_t axis, vec3_t v)
{
	vec3_t          b;
	int32_t                 j, k;

	b[0] = s * gl_farclip.value / sqrt(3.0);
	b[1] = t * gl_farclip.value / sqrt(3.0);
	b[2] = gl_farclip.value / sqrt(3.0);

	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];
	}
}

/*
=============
Sky_GetTexCoord
=============
*/
void Sky_GetTexCoord(vec3_t v, float speed, float *s, float *t)
{
	vec3_t  dir;
	float   length, scroll;

	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;

	scroll = cl.time * speed;
	scroll -= (int32_t)scroll & ~127;

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

/*
===============
Sky_DrawFaceQuad
===============
*/
void Sky_DrawFaceQuad(glpoly_t *p)
{
	float   s, t;
	float   *v;
	int32_t         i;

	if(gl_mtexable && r_skyalpha.value >= 1.0)
	{
		GL_Bind(solidskytexture);
		GL_EnableMultitexture();
		GL_Bind(alphaskytexture);
		glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

		glBegin(GL_QUADS);
		for(i = 0, v = p->verts[0] ; i < 4 ; i++, v += VERTEXSIZE)
		{
			Sky_GetTexCoord(v, 8, &s, &t);
			GL_MTexCoord2fFunc(GL_TEXTURE0_ARB, s, t);
			Sky_GetTexCoord(v, 16, &s, &t);
			GL_MTexCoord2fFunc(GL_TEXTURE1_ARB, s, t);
			glVertex3fv(v);
		}
		glEnd();

		GL_DisableMultitexture();

		rs_skypolys++;
		rs_skypasses++;
	}
	else
	{
		GL_Bind(solidskytexture);

		if(r_skyalpha.value < 1.0)
			glColor3f(1, 1, 1);

		glBegin(GL_QUADS);
		for(i = 0, v = p->verts[0] ; i < 4 ; i++, v += VERTEXSIZE)
		{
			Sky_GetTexCoord(v, 8, &s, &t);
			glTexCoord2f(s, t);
			glVertex3fv(v);
		}
		glEnd();

		GL_Bind(alphaskytexture);
		glEnable(GL_BLEND);

		if(r_skyalpha.value < 1.0)
			glColor4f(1, 1, 1, r_skyalpha.value);

		glBegin(GL_QUADS);
		for(i = 0, v = p->verts[0] ; i < 4 ; i++, v += VERTEXSIZE)
		{
			Sky_GetTexCoord(v, 16, &s, &t);
			glTexCoord2f(s, t);
			glVertex3fv(v);
		}
		glEnd();

		glDisable(GL_BLEND);

		rs_skypolys++;
		rs_skypasses += 2;
	}

	if(Fog_GetDensity() > 0 && skyfog > 0)
	{
		float *c;

		c = Fog_GetColor();
		glEnable(GL_BLEND);
		glDisable(GL_TEXTURE_2D);
		glColor4f(c[0], c[1], c[2], CLAMP(0.0, skyfog, 1.0));

		glBegin(GL_QUADS);
		for(i = 0, v = p->verts[0] ; i < 4 ; i++, v += VERTEXSIZE)
			glVertex3fv(v);
		glEnd();

		glColor3f(1, 1, 1);
		glEnable(GL_TEXTURE_2D);
		glDisable(GL_BLEND);

		rs_skypasses++;
	}
}

/*
==============
Sky_DrawFace
==============
*/

void Sky_DrawFace(int32_t axis)
{
	glpoly_t        *p;
	vec3_t          verts[4];
	int32_t                 i, j, start;
	float           di, qi, dj, qj;
	vec3_t          vup, vright, temp, temp2;

	Sky_SetBoxVert(-1.0, -1.0, axis, verts[0]);
	Sky_SetBoxVert(-1.0,  1.0, axis, verts[1]);
	Sky_SetBoxVert(1.0,   1.0, axis, verts[2]);
	Sky_SetBoxVert(1.0,  -1.0, axis, verts[3]);

	start = Hunk_LowMark();
	p = (glpoly_t *) Hunk_Alloc(sizeof(glpoly_t));

	VectorSubtract(verts[2], verts[3], vup);
	VectorSubtract(verts[2], verts[1], vright);

	di = q_max((int32_t)r_sky_quality.value, 1);
	qi = 1.0 / di;
	dj = (axis < 4) ? di * 2 : di; //subdivide vertically more than horizontally on skybox sides
	qj = 1.0 / dj;

	for(i = 0; i < di; i++)
	{
		for(j = 0; j < dj; j++)
		{
			if(i * qi < skymins[0][axis] / 2 + 0.5 - qi || i * qi > skymaxs[0][axis] / 2 + 0.5 ||
			                j * qj < skymins[1][axis] / 2 + 0.5 - qj || j * qj > skymaxs[1][axis] / 2 + 0.5)
				continue;

			//if (i&1 ^ j&1) continue; //checkerboard test
			VectorScale(vright, qi * i, temp);
			VectorScale(vup, qj * j, temp2);
			VectorAdd(temp, temp2, temp);
			VectorAdd(verts[0], temp, p->verts[0]);

			VectorScale(vup, qj, temp);
			VectorAdd(p->verts[0], temp, p->verts[1]);

			VectorScale(vright, qi, temp);
			VectorAdd(p->verts[1], temp, p->verts[2]);

			VectorAdd(p->verts[0], temp, p->verts[3]);

			Sky_DrawFaceQuad(p);
		}
	}
	Hunk_FreeToLowMark(start);
}

/*
==============
Sky_DrawSkyLayers

draws the old-style scrolling cloud layers
==============
*/
void Sky_DrawSkyLayers(void)
{
	int32_t i;

	if(r_skyalpha.value < 1.0)
		glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

	for(i = 0 ; i < 6 ; i++)
		if(skymins[0][i] < skymaxs[0][i] && skymins[1][i] < skymaxs[1][i])
			Sky_DrawFace(i);

	if(r_skyalpha.value < 1.0)
		glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
}

/*
==============
Sky_DrawSky

called once per frame before drawing anything else
==============
*/
void Sky_DrawSky(void)
{
	int32_t                         i;

	//in these special render modes, the sky faces are handled in the normal world/brush renderer
	if(r_drawflat_cheatsafe || r_lightmap_cheatsafe)
		return;

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

	//
	// process world and bmodels: draw flat-shaded sky surfs, and update skybounds
	//
	Fog_DisableGFog();
	glDisable(GL_TEXTURE_2D);
	if(Fog_GetDensity() > 0)
		glColor3fv(Fog_GetColor());
	else
		glColor3fv(skyflatcolor);
	Sky_ProcessTextureChains();
	Sky_ProcessEntities();
	glColor3f(1, 1, 1);
	glEnable(GL_TEXTURE_2D);

	//
	// render slow sky: cloud layers or skybox
	//
	if(!r_fastsky.value && !(Fog_GetDensity() > 0 && skyfog >= 1))
	{
		glDepthFunc(GL_GEQUAL);
		glDepthMask(0);

		if(skybox_name[0])
			Sky_DrawSkyBox();
		else
			Sky_DrawSkyLayers();

		glDepthMask(1);
		glDepthFunc(GL_LEQUAL);
	}

	Fog_EnableGFog();
}