/*
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_sky.c

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


int		iskyspeed = 8;
int		iskyspeed2 = 2;
float	skyspeed, skyspeed2;

float	skyshift;

byte	*r_skysource;
int		r_skymade;


// TODO: clean up these routines

byte	bottomsky[128*131];
byte	bottommask[128*131];
byte	newsky[128*256];	// newsky and topsky both pack in here, 128 bytes
							//  of newsky on the left of each scan, 128 bytes
							//  of topsky on the right, because the low-level
							//  drawers need 256-byte scan widths

//A sky texture is 256*128, with the right side being a masked overlay
void R_InitSky (miptex_t *mt) {
	int i, j;
	byte *src;

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

	for (i = 0; i < 128; i++) {
		for (j = 0; j < 128; j++)
			newsky[(i*256) + j + 128] = src[i*256 + j + 128];
	}

	for (i = 0; i < 128; i++) {
		for (j = 0; j < 131; j++) {
			if (src[i*256 + (j & 0x7F)]) {
				bottomsky[(i*131) + j] = src[i*256 + (j & 0x7F)];
				bottommask[(i*131) + j] = 0;
			} else {
				bottomsky[(i*131) + j] = 0;
				bottommask[(i*131) + j] = 0xff;
			}
		}
	}
	r_skysource = newsky;
}

void R_MakeSky (void) {
	int x, y, ofs, baseofs, xshift, yshift;
	unsigned *pnewsky;
	static int xlast = -1, ylast = -1;

	xshift = skyshift;
	yshift = skyshift;

	if ((xshift == xlast) && (yshift == ylast))
		return;

	xlast = xshift;
	ylast = yshift;
	
	pnewsky = (unsigned *)&newsky[0];

	for (y = 0; y < SKYSIZE; y++) {
		baseofs = ((y+yshift) & SKYMASK) * 131;

// FIXME: clean this up
#if UNALIGNED_OK

		for (x = 0; x < SKYSIZE; x += 4) {
			ofs = baseofs + ((x+xshift) & SKYMASK);

			// PORT: unaligned dword access to bottommask and bottomsky
			*pnewsky = (*(pnewsky + (128 / sizeof (unsigned))) & *(unsigned *) &bottommask[ofs]) | *(unsigned *) &bottomsky[ofs];
			pnewsky++;
		}

#else
		for (x = 0; x < SKYSIZE; x++) {
			ofs = baseofs + ((x+xshift) & SKYMASK);

			*(byte *)pnewsky = (*((byte *)pnewsky + 128) & *(byte *)&bottommask[ofs]) | *(byte *)&bottomsky[ofs];
			pnewsky = (unsigned *)((byte *)pnewsky + 1);
		}

#endif
		pnewsky += 128 / sizeof (unsigned);
	}

	r_skymade = 1;
}

void R_GenSkyTile (void *pdest) {
	int x, y, ofs, baseofs, xshift, yshift;
	unsigned *pnewsky, *pd;

	xshift = skyshift;
	yshift = skyshift;

	pnewsky = (unsigned *)&newsky[0];
	pd = (unsigned *)pdest;

	for (y = 0; y < SKYSIZE; y++) {
		baseofs = ((y+yshift) & SKYMASK) * 131;

// FIXME: clean this up
#if UNALIGNED_OK
		for (x = 0; x < SKYSIZE; x += 4) {
			ofs = baseofs + ((x+xshift) & SKYMASK);

			// PORT: unaligned dword access to bottommask and bottomsky

			*pd = (*(pnewsky + (128 / sizeof (unsigned))) & *(unsigned *)&bottommask[ofs]) |*(unsigned *)&bottomsky[ofs];
			pnewsky++;
			pd++;
		}

#else
		for (x = 0; x < SKYSIZE; x++) {
			ofs = baseofs + ((x+xshift) & SKYMASK);

			*(byte *)pd = (*((byte *)pnewsky + 128) & *(byte *)&bottommask[ofs]) | *(byte *)&bottomsky[ofs];
			pnewsky = (unsigned *)((byte *)pnewsky + 1);
			pd = (unsigned *)((byte *)pd + 1);
		}

#endif

		pnewsky += 128 / sizeof (unsigned);
	}
}

void R_SetSkyFrame (void) {
	int g, s1, s2;
	float temp, skytime;

	skyspeed = iskyspeed;
	skyspeed2 = iskyspeed2;

	g = GreatestCommonDivisor (iskyspeed, iskyspeed2);
	s1 = iskyspeed / g;
	s2 = iskyspeed2 / g;
	temp = SKYSIZE * s1 * s2;

	skytime = r_refdef2.time - ((int)(r_refdef2.time / temp) * temp);
	skyshift = skytime * skyspeed;	

	r_skymade = 0;
}
