/* Copyright Jeff Lassahn.  See graph3d.tex for details. */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "render.h"
#include "liftio.h"

typedef struct tagclouds {
	float start;
	float stop;
	PIX_RGB32 fog;
	PIX_RGB32 skytop;
	PIX_RGB32 skybottom;
	//FIXME lighting control
} CLOUDS;

#define FOG_STRENGTH 0.5
#define MIN_VIS 1000.0
#define MAX_CLEAR 10000.0
#define MAX_VIS 15000.0
#define HAZE_DEPTH 5.0

void SetFog(PG_ENVIRONMENT *env,CLOUDS *cl,float z,PIX_RGB32 sky[513])
{
PIX_RGB32 fogcol;
PIX_RGB32 top;
PIX_RGB32 bottom;
int i;
float f,depth;

	fogcol.red=(env->lights[0].red+env->lights[1].red*env->lights[1].pos.z)*
						cl->fog.red;
	fogcol.green=(env->lights[0].green+env->lights[1].green*env->lights[1].pos.z)*
						cl->fog.green;
	fogcol.blue=(env->lights[0].blue+env->lights[1].blue*env->lights[1].pos.z)*
						cl->fog.blue;

	top.red=env->lights[0].red*cl->skytop.red;
	top.green=env->lights[0].green*cl->skytop.green;
	top.blue=env->lights[0].blue*cl->skytop.blue;
	
	bottom.red=(env->lights[0].red+env->lights[1].red*2)*
						cl->skybottom.red;
	bottom.green=(env->lights[0].green+env->lights[1].green*2)*
						cl->skybottom.green;
	bottom.blue=(env->lights[0].blue+env->lights[1].blue*2)*
						cl->skybottom.blue;

	if (z<cl->stop) {
		depth=(cl->start-cl->stop)*FOG_STRENGTH;
	}
	else {
		depth=(cl->start-z)*FOG_STRENGTH;
	}
	if (depth<HAZE_DEPTH)
		depth=HAZE_DEPTH;

	if (env->fog) {
		env->fog->col=fogcol;
		env->fog->start_dist=HAZE_DEPTH*MAX_CLEAR/depth;
		env->fog->stop_dist=MIN_VIS+HAZE_DEPTH*(MAX_VIS-MIN_VIS)/depth;
	}

	for (i=1;i<257;i++) {
		sky[i+256].red=(bottom.red*(256-i)+top.red*(i-1))>>8;
		sky[i+256].green=(bottom.green*(256-i)+top.green*(i-1))>>8;
		sky[i+256].blue=(bottom.blue*(256-i)+top.blue*(i-1))>>8;

		f=depth/i;
		if (f>1.0)
			f=1.0;

		sky[i+256].red=f*fogcol.red+(1.0-f)*sky[i+256].red;
		sky[i+256].green=f*fogcol.green+(1.0-f)*sky[i+256].green;
		sky[i+256].blue=f*fogcol.blue+(1.0-f)*sky[i+256].blue;
	}
	for (i=0;i<257;i++) {
		sky[i]=fogcol;
	}
}

#define PI 3.1415926
#define SECS_PER_DAY (60*60*24)
void SetLights(int seconds,PG_LIGHT lights[2])
{
float ct,st;
	ct=-cos(seconds*2.0*PI/SECS_PER_DAY);
	st=sin(seconds*2.0*PI/SECS_PER_DAY);

	/* ambient light.  brightest at noon */
	lights[0].red=0.2+0.3*ct+0.3*ct*ct;
	lights[0].green=0.2+0.3*ct+0.3*ct*ct;
	lights[0].blue=0.2+0.3*ct+0.3*ct*ct;

	/* directed light.  changes direction, intensity, and color as the
		day progresses. */
	lights[1].pos.x=st;
	lights[1].pos.y=0;

	/* the new value of st is st^6, which is close to 1 near sunrise and sunset, close to
		0 otherwise. */
	st=st*st;
	st=st*st*st;
	if (ct>0.0) { /* if the sun is above the horizon */
		lights[1].pos.z=ct;

		lights[1].red=0.2+0.4*st;
		lights[1].green=0.2+0.1*st;
		lights[1].blue=0.2;
	}
	else {
		lights[1].pos.z=-ct;

		lights[1].red=0.6*st;
		lights[1].green=0.3*st;
		lights[1].blue=0.2*st;
	}
}