#include <stdio.h>
#include <math.h>
#include <sys/types.h>
#include <malloc.h>
#include "cloud.h"

/*
 * The QAEB procedural ray tracing routine.
 *
 * Initialization routine.
 *
 * Copyright 1998 F. Kenton Musgrave
 * All rights reserved
 */


extern Color		*scanline;
extern FILE		*outfile;
extern unsigned long	samples;
extern unsigned long	hits;


/*
 * Initialize the various variables needed for the rendering.
 */
Init( int argc, char *argv[], OptionsType *options, CameraType *camera, 
      Light *light, Color *background, double *octaves_scalar )
{
	int	i;
	double	frequency;

	if ( argc < 2 ) {
		fprintf(stderr, 
			"usage: %s outfile\n", argv[0]);
		exit (-1);
	}

	if ( (outfile = fopen(argv[1], "w")) == NULL ) {
		fprintf(stderr, 
			"%s: fatal error: cannot open file %s\n",
			argv[0], argv[1]);
		exit (-1);
	}

	/* set default variable values */
	Set_Defaults( options, camera, light, background );
	/* get user input */
	Read_Input( argc, argv, options, camera, light );
	/* initialize viewing parameters */
	Init_Camera( camera );

	/* initialize tables for Noise2() and Noise3() functions */
	Init_Noise();

	/* allocate memory for scanline */
	scanline = (Color *)calloc( (size_t)camera->hres,
				    (size_t)sizeof( Color ) );

	/* Initialize the magic number that relates distance to octaves */
	*octaves_scalar = -LOG2(tan(DEGTORAD(0.5*camera->hfov / camera->hres)))
			  - 3.0;	/* relates Noise() to Nyquist limit */

#ifdef PPM
	/* Write the PPM image file header */
	fprintf( outfile, "P6 %d %d %d\n", camera->hres, camera->vres, 255 );
	fflush( outfile );
#endif

} /* Init() */


/*
 * Initialize default variable values.
 */
Set_Defaults( OptionsType *options, CameraType *camera, Light *light, 
	      Color *background )
{

        camera->eyep.x = 0.0;		/* position the camera */
        camera->eyep.x = 0.25;		/* right eye */
        camera->eyep.x = -.25;		/* left eye */
        camera->eyep.y = 0.0;
        camera->eyep.z = 0.0;

        camera->look_pt.x = 0.0;	/* looking at... */
        camera->look_pt.y = 6.0;
        camera->look_pt.z = 0.0;

        camera->up_dir.x = 0.0;		/* camera "up" vector */
        camera->up_dir.y = 0.0;
        camera->up_dir.z = 1.0;

        camera->hfov = 25.0;		/* set horizontal field of view */
        camera->vfov = 20.0;		/* set vertical field of view */

	/* for cumulus cloud experiment */
	camera->hres = 256;		/* set horizontal resolution */
	camera->vres = 208;		/* set vertical resolution */

	camera->near_clip= 4.25;  	/* set near clipping distance */
	camera->far_clip=  7.0;		/* set far clipping distance */
	options->shad_clip_dist = 1.5;	/* slow but accurate */
	options->shad_clip_dist = 1.0;	/* pretty accurate */

	options->threshold = 0.0;	/* crossover from air to cloud */
	options->density_scale = 100.0;	/* for volcanic cloud */
	options->density_scale = 35.0;	/* scales cloud density */

	options->step_scale = 3.0;	/* scalar for the increments */
	options->shadstep_scale = 2.0;	/* scalar for the shadow ray steps */
	options->gamma = 1.9;		/* for film recorder */
	options->gamma = 2.4;		/* set image gamma */
	options->noise = 1./255.;	/* amount of noise to add to pixels */

	light->direction.x =  1.0;	/* set up some fixed light direction */
	light->direction.y = -1.0;
	light->direction.z =  1.0;
	Normalize( &light->direction );
	light->color.r = 1.10;		/* determine light color */
	light->color.g = 1.05;
	light->color.b = 1.00;

	background->r = 0.0;		/* set background color */
	background->g = 0.0;
	background->b = 1.0;

	hits = 0;			/* initialize statistics storage */
	samples = 0;

} /* Set_Defaults() */


/*
 * Read input to initialize the various variables needed for the rendering.
 *
 * (Current a straw-horse routine.)
 */
Read_Input( int argc, char *argv[], OptionsType *options, CameraType *camera, 
      	    Light *light )
{
	return;
} /* Read_Input() */


Init_Camera( CameraType *camera )
{

	/* point the camera */
        camera->view_dir.x = camera->look_pt.x - camera->eyep.x;
        camera->view_dir.y = camera->look_pt.y - camera->eyep.y;
        camera->view_dir.z = camera->look_pt.z - camera->eyep.z;
	NORM( (&camera->view_dir) );

	/* calculate the lateral screeen dir */
	CROSS( camera->view_dir, camera->up_dir, (&camera->right_dir) );
	NORM( (&camera->right_dir) );

	/* recalculate the screeen "up" dir */
	CROSS( camera->right_dir, camera->view_dir, (&camera->up_dir) );
	NORM( (&camera->up_dir) );


	/* calculate pixel dimensions at unit distance */
        camera->pix_width = 2 * tan(DEGTORAD(0.5*camera->hfov)) / camera->hres;
        camera->pix_height = 2 * tan(DEGTORAD(0.5*camera->vfov)) / camera->vres;

	/* 
	 * Calculate the dir of ray through pixel [0,0],
	 * from which all other screen rays are offset.
	 */
        camera->corner_ray.x = camera->view_dir.x - 
                   0.5*camera->hres * camera->pix_width * camera->right_dir.x -
                   0.5*camera->vres * camera->pix_height * camera->up_dir.x;
        camera->corner_ray.y = camera->view_dir.y - 
                   0.5*camera->hres * camera->pix_width * camera->right_dir.y -
                   0.5*camera->vres * camera->pix_height * camera->up_dir.y;
        camera->corner_ray.z = camera->view_dir.z - 
                   0.5*camera->hres * camera->pix_width * camera->right_dir.z -
                   0.5*camera->vres * camera->pix_height * camera->up_dir.z;

} /* Init_Camera() */


/*
 * Take care of whatever hideous nonsense is required before we exit main().
 */
Cleanup( Color *scanline, FILE *outfile )
{
		/* free scanline memory */
	free( scanline );

		/* close up the image file */
	fflush( outfile );	/* flush the buffer first */
	fclose( outfile );

} /* Cleanup() */