/******************************************************************************
 * Copyright (C) 1986-2005 mental images GmbH, Fasanenstr. 81, D-10623 Berlin,
 * Germany. All rights reserved.
 * Portions Copyright (C) 1997-2005 Alias Systems Corp.
 ******************************************************************************
/*
// Copyright (C) Alias Systems, a division of Silicon Graphics Limited and/or
// its licensors ("Alias").  All rights reserved.  These coded instructions,
// statements, computer programs, and/or related material (collectively, the
// "Material") contain unpublished information proprietary to Alias, which is
// protected by Canadian and US federal copyright law and by international
// treaties.  This Material may not be disclosed to third parties, or be
// copied or duplicated, in whole or in part, without the prior written
// consent of Alias.  ALIAS HEREBY DISCLAIMS ALL WARRANTIES RELATING TO THE
// MATERIAL, INCLUDING, WITHOUT LIMITATION, ANY AND ALL EXPRESS OR IMPLIED
// WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.  IN NO EVENT SHALL ALIAS BE LIABLE FOR ANY DAMAGES
// WHATSOEVER, WHETHER DIRECT, INDIRECT, SPECIAL, OR PUNITIVE, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, OR IN EQUITY,
// ARISING OUT OF OR RELATED TO THE ACCESS TO, USE OF, OR RELIANCE UPON THE
// MATERIAL.
*/

/******************************************************************************
 * This file shows how to write a mental ray material shader
 * that uses "emit diffuse" and "emit specular" of lights.
 *
 * This example takes mib_illum_phong as a starting point
 * (can be found at <maya install directory>/devkit/mentalray/shaders/public-baseshaders/basephong.c)
 * and adds maya specific codes.
 * Changes to the original source code
 * can be found by searching the keyword MAYA
 *
 * A header file mayaapi.h should be included which can be found at
 * <maya install directory>/devkit/mentalray/include
 * If Windows is the working environment, 
 * mayabase.lib needs to be linked in addition to shader.lib.
 * Both libraries are located at
 * <maya install directory>/devkit/mentalray/lib/nt
 *****************************************************************************/

#ifdef HPUX
#pragma OPT_LEVEL 1	/* workaround for HP/UX optimizer bug, +O2 and +O3 */
#endif

#include <stdio.h>
#include <stdlib.h>		/* for abs */
#include <float.h>		/* for FLT_MAX */
#include <math.h>
#include <string.h>
#include <assert.h>
#include "shader.h"


/******************************************************************************
 * MAYA
 *
 * Necessary header file
 * to access maya specific information
 *****************************************************************************/
#include "mayaapi.h"


struct mayaEmitLight_mib_illum_phong {
	/* mib_illum_phong parameters */
	miColor		ambience;	
	miColor		ambient;	
	miColor		diffuse;	
	miColor		specular;	
	miScalar	exponent;	
	int			mode;           
	int			i_light;	
	int			n_light;	
	miTag		light[1];
};


DLLEXPORT int mayaEmitLight_mib_illum_phong_version(void) {return(2);}


/*
 * Modification of mib_illum_phong
 * 
 */
DLLEXPORT miBoolean mayaEmitLight_mib_illum_phong(
	miColor		*result,
	miState		*state,
	struct mayaEmitLight_mib_illum_phong *paras)
{
	miColor		*ambi, *diff, *spec;
	miTag		*light;		/* tag of light instance */
	int			n_l;		/* number of light sources */
	int			i_l;		/* offset of light sources */
	int			m;		/* light mode: 0=all, 1=incl, 2=excl */
	int			n;		/* light counter */
	int			samples;	/* # of samples taken */
	miColor		color;		/* color from light source */
	miColor		sum;		/* summed sample colors */
	miVector	dir;		/* direction towards light */
	miScalar	dot_nl;		/* dot prod of normal and dir */
	miScalar	expo;		/* Phong exponent (cosine power) */
	miScalar	s;		/* amount of specular reflection */

	
	/******************************************************************************
	 * MAYA
	 *
	 * Pointers to access the shader state
	 *****************************************************************************/
	miBoolean *emitDiffuse, *emitSpecular;
       
	/* check for illegal calls */
	if (state->type == miRAY_SHADOW || state->type == miRAY_DISPLACE ) {
		return(miFALSE);
	}
 
	ambi =  mi_eval_color(&paras->ambient);
	diff =  mi_eval_color(&paras->diffuse);
	spec =  mi_eval_color(&paras->specular);
	expo = *mi_eval_scalar(&paras->exponent);
	m    = *mi_eval_integer(&paras->mode);

	*result    = *mi_eval_color(&paras->ambience);	/* ambient term */
	result->r *= ambi->r;
	result->g *= ambi->g;
	result->b *= ambi->b;

	n_l   = *mi_eval_integer(&paras->n_light);
	i_l   = *mi_eval_integer(&paras->i_light);
	light =  mi_eval_tag(paras->light) + i_l;

	if (m == 1)		/* modify light list (inclusive mode) */
		mi_inclusive_lightlist(&n_l, &light, state);
	else if (m == 2)	/* modify light list (exclusive mode) */
		mi_exclusive_lightlist(&n_l, &light, state);

	/* Loop over all light sources */
	for (n=0; n < n_l; n++, light++) {
		sum.r = sum.g = sum.b = 0;
		samples = 0;
		while (mi_sample_light(&color, &dir, &dot_nl, state,
						*light, &samples)) {
			/******************************************************************************
			* MAYA
			*
			* Get pointers to the shader state variables.
			*
			* mayabase_stateitem_get returns pointer to
			* specified MbStateItem in the shader state.
			* MBSI_LIGHTDIFFUSE and MBSI_LIGHTSPECULAR
			* contains information about 
			* whether the light emits diffuse and specualr.
			* The variable-length parameter should terminated
			* with MBSI_NULL.
			*
			* Light shader sets the shader state value
			* to inform that whether the light shader
			* emits diffuse and specular lights.
			*****************************************************************************/
			mayabase_stateitem_get(state, 
				MBSI_LIGHTDIFFUSE,	&emitDiffuse,
				MBSI_LIGHTSPECULAR, &emitSpecular,
				MBSI_NULL
			);

			/******************************************************************************
			* MAYA
			*
			* Add diffuse component
			* only if the light emits diffuse lights
			*****************************************************************************/
			if( *emitDiffuse ) {
				/* Lambert's cosine law */
				sum.r += dot_nl * diff->r * color.r;
				sum.g += dot_nl * diff->g * color.g;
				sum.b += dot_nl * diff->b * color.b;
			}

			/******************************************************************************
			* MAYA
			*
			* Add specular component
			* only if the light emits specular lights
			*****************************************************************************/
			if( *emitSpecular ) {
				/* Phong's cosine power */
				s = mi_phong_specular(expo, state, &dir);
				if (s > 0.0) {
					sum.r += s * spec->r * color.r;
					sum.g += s * spec->g * color.g;
					sum.b += s * spec->b * color.b;
				}
			}
		}
		if (samples) {
			result->r += sum.r / samples;
			result->g += sum.g / samples;
			result->b += sum.b / samples;
		}
	}

	/* add contribution from indirect illumination (caustics) */
	mi_compute_irradiance(&color, state);
	result->r += color.r * diff->r;
	result->g += color.g * diff->g;
	result->b += color.b * diff->b;
	result->a  = 1;
	return(miTRUE);

}