/*
	r_light.c

	(description)

	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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

	$Id$
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "r_local.h"

int         r_dlightframecount;


/*
==================
R_AnimateLight
==================
*/
void
R_AnimateLight (void)
{
	int         i, j, k;

//
// light animations
// 'm' is normal light, 'a' is no light, 'z' is double bright
	i = (int) (cl.time * 10);
	for (j = 0; j < MAX_LIGHTSTYLES; j++) {
		if (!cl_lightstyle[j].length) {
			d_lightstylevalue[j] = 256;
			continue;
		}
		k = i % cl_lightstyle[j].length;
		k = cl_lightstyle[j].map[k] - 'a';
		k = k * 22;
		d_lightstylevalue[j] = k;
	}
}


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

DYNAMIC LIGHTS

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

/*
=============
R_MarkLights
=============
*/
void
R_MarkLights (vec3_t lightorigin, dlight_t *light, int bit, mnode_t *node)
{
	mplane_t   *splitplane;
	float       dist;
	msurface_t *surf;
	int         i;

	if (node->contents < 0)
		return;

	splitplane = node->plane;
	dist = DotProduct (lightorigin, splitplane->normal) - splitplane->dist;

	if (dist > light->radius) {
		R_MarkLights (lightorigin, light, bit, node->children[0]);
		return;
	}
	if (dist < -light->radius) {
		R_MarkLights (lightorigin, light, bit, node->children[1]);
		return;
	}
// mark the polygons
	surf = cl.worldmodel->surfaces + node->firstsurface;
	for (i = 0; i < node->numsurfaces; i++, surf++) {
		if (surf->dlightframe != r_dlightframecount) {
			surf->dlightbits = 0;
			surf->dlightframe = r_dlightframecount;
		}
		surf->dlightbits |= bit;
	}

	R_MarkLights (lightorigin, light, bit, node->children[0]);
	R_MarkLights (lightorigin, light, bit, node->children[1]);
}


/*
=============
R_PushDlights
=============
*/
void
R_PushDlights (vec3_t entorigin)
{
	int         i;
	dlight_t   *l;
	vec3_t      lightorigin;

	r_dlightframecount = r_framecount + 1;	// because the count hasn't
	// advanced yet for this frame
	l = cl_dlights;

	for (i = 0; i < MAX_DLIGHTS; i++, l++) {
		if (l->die < cl.time || !l->radius)
			continue;
		VectorSubtract (l->origin, entorigin, lightorigin);
		R_MarkLights (lightorigin, l, 1 << i, cl.worldmodel->nodes);
	}
}


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

LIGHT SAMPLING

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

int
RecursiveLightPoint (mnode_t *node, vec3_t start, vec3_t end)
{
	int         r;
	float       front, back, frac;
	int         side;
	mplane_t   *plane;
	vec3_t      mid;
	msurface_t *surf;
	int         s, t, ds, dt;
	int         i;
	mtexinfo_t *tex;
	byte       *lightmap;
	unsigned int scale;
	int         maps;

	if (node->contents < 0)
		return -1;						// didn't hit anything

// calculate mid point

// FIXME: optimize for axial
	plane = node->plane;
	front = DotProduct (start, plane->normal) - plane->dist;
	back = DotProduct (end, plane->normal) - plane->dist;
	side = front < 0;

	if ((back < 0) == side)
		return RecursiveLightPoint (node->children[side], start, end);

	frac = front / (front - back);
	mid[0] = start[0] + (end[0] - start[0]) * frac;
	mid[1] = start[1] + (end[1] - start[1]) * frac;
	mid[2] = start[2] + (end[2] - start[2]) * frac;

// go down front side   
	r = RecursiveLightPoint (node->children[side], start, mid);
	if (r >= 0)
		return r;						// hit something

	if ((back < 0) == side)
		return -1;						// didn't hit anything

// check for impact on this node

	surf = cl.worldmodel->surfaces + node->firstsurface;
	for (i = 0; i < node->numsurfaces; i++, surf++) {
		if (surf->flags & SURF_DRAWTILED)
			continue;					// no lightmaps

		tex = surf->texinfo;

		s = DotProduct (mid, tex->vecs[0]) + tex->vecs[0][3];
		t = DotProduct (mid, tex->vecs[1]) + tex->vecs[1][3];;

		if (s < surf->texturemins[0] || t < surf->texturemins[1])
			continue;

		ds = s - surf->texturemins[0];
		dt = t - surf->texturemins[1];

		if (ds > surf->extents[0] || dt > surf->extents[1])
			continue;

		if (!surf->samples)
			return 0;

		ds >>= 4;
		dt >>= 4;

		lightmap = surf->samples;
		r = 0;
		if (lightmap) {

			lightmap += dt * ((surf->extents[0] >> 4) + 1) + ds;

			for (maps = 0; maps < MAXLIGHTMAPS && surf->styles[maps] != 255;
				 maps++) {
				scale = d_lightstylevalue[surf->styles[maps]];
				r += *lightmap * scale;
				lightmap += ((surf->extents[0] >> 4) + 1) *
					((surf->extents[1] >> 4) + 1);
			}

			r >>= 8;
		}

		return r;
	}

// go down back side
	return RecursiveLightPoint (node->children[!side], mid, end);
}

int
R_LightPoint (vec3_t p)
{
	vec3_t      end;
	int         r;

	if (!cl.worldmodel->lightdata)
		return 255;

	end[0] = p[0];
	end[1] = p[1];
	end[2] = p[2] - 2048;

	r = RecursiveLightPoint (cl.worldmodel->nodes, p, end);

	if (r == -1)
		r = 0;

	if (r < r_refdef.ambientlight)
		r = r_refdef.ambientlight;

	return r;
}