/*
 * Copyright (c) 1993-1995 Argonaut Technologies Limited. All rights reserved.
 *
 * $Id: light24.c 1.5 1995/03/01 15:26:08 sam Exp $
 * $Locker:  $
 *
 * Bits of the lighting model for true colour pixels
 */

#include "fw.h"
#include "shortcut.h"
#include "brassert.h"

static char rscid[] = "$Id: light24.c 1.5 1995/03/01 15:26:08 sam Exp $";

/*
 * Evaluate the vertex lighting function, and return a value
 * for uniform face rendering
 */
br_uint_32 BR_SURFACE_CALL LightingFaceColour(br_vertex *v, br_face *fp, int reversed)
{
	br_scalar comp[NUM_COMPONENTS];
	br_fvector3 rev_normal;

	if(!reversed) {
		fw.surface_fn(v, &fp->n, comp);

	} else {

		BrFVector3Negate(&rev_normal,&fp->n);
		fw.surface_fn(v, &rev_normal, comp);
	}

	return BR_COLOUR_RGB(BrScalarToInt(comp[C_R]),
					BrScalarToInt(comp[C_G]),
					BrScalarToInt(comp[C_B])) ;
}

/*
 * Lighting function for unlit colour
 */
void BR_SURFACE_CALL LightingColourCopyMaterial(br_vertex *v, br_fvector3 *n, br_scalar *comp)
{
	comp[C_R]=BrIntToScalar(BR_RED(fw.material->colour));
	comp[C_G]=BrIntToScalar(BR_GRN(fw.material->colour));
	comp[C_B]=BrIntToScalar(BR_BLU(fw.material->colour));
}

/*
 * Lighting function for prelit colour
 */
void BR_SURFACE_CALL LightingColourCopyVertex(br_vertex *v, br_fvector3 *n, br_scalar *comp)
{
	comp[C_R] = BrIntToScalar(v->red);
	comp[C_G] = BrIntToScalar(v->grn);
	comp[C_B] = BrIntToScalar(v->blu);
}

/*
 * Work out 3 component lighting given:
 * 	A point
 *	A normal
 *  A material
 *
 * Examines all active lights and accumulates lighting from each light
 *
 * Writes results into
 *	comp[C_R]
 *	comp[C_G]
 *	comp[C_B]
 */
void BR_SURFACE_CALL LightingColour(br_vertex *v, br_fvector3 *n, br_scalar *comp)
{
	br_active_light *alp;
	int i;
	br_vector3 vp;
	br_vector3 vn;
	br_fvector3 fvn;

	br_scalar lcomp[NUM_L_COMPONENTS];
	br_scalar r,g,b;

	r=g=b=BR_SCALAR(0.0);

	fw.eye_l=fw.eye_m_normalised;
	alp=fw.active_lights_model;

	/*
	 * Ambient component
	 */
	r=BR_MUL(fw.material->ka,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
	g=BR_MUL(fw.material->ka,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
	b=BR_MUL(fw.material->ka,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

	/*
	 * Accumulate intensities for each active light in model space
	 */
	alp=fw.active_lights_model;
	for(i=0;i<fw.nactive_lights_model;i++,alp++)
	{
		alp->light_sub_function(&v->p, n, alp, lcomp);

		r+=lcomp[L_R];
		g+=lcomp[L_G];
		b+=lcomp[L_B];
	}

	/*
	 * See if any lights are to be calculated in view space
	 */
	if(fw.nactive_lights_view) {
		BrMatrix34ApplyP(&vp, &v->p, &fw.model_to_view);
		BrMatrix34TApplyFV(&vn, n, &fw.view_to_model);
		BrFVector3Normalise(&fvn, &vn);

		fw.eye_l.v[0] = BR_SCALAR(0);
		fw.eye_l.v[1] = BR_SCALAR(0);
		fw.eye_l.v[2] = BR_SCALAR(1);

		/*
		 * ... and accumulate
		 */
		alp = fw.active_lights_view;
		for(i=0; i < fw.nactive_lights_view; i++, alp++)
		{
			alp->light_sub_function(&vp, &fvn, alp, lcomp);
			r+=lcomp[L_R];
			g+=lcomp[L_G];
			b+=lcomp[L_B];
		}
	}

	/*
	 * Scale and clamp to final range
	 */
	comp[C_R] = BR_MUL(r,BR_SCALAR(256));
	comp[C_G] = BR_MUL(g,BR_SCALAR(256));
	comp[C_B] = BR_MUL(b,BR_SCALAR(256));

#define RGB_MAX BR_SCALAR(254.0)
#define RGB_MIN BR_SCALAR(1.0)

	if(comp[C_R] >= RGB_MAX)
		comp[C_R] = RGB_MAX;
	else if(comp[C_R] < RGB_MIN)
		comp[C_R] = RGB_MIN;

	if(comp[C_G] >= RGB_MAX)
		comp[C_G] = RGB_MAX;
	else if(comp[C_G] < RGB_MIN)
		comp[C_G] = RGB_MIN;

	if(comp[C_B] >= RGB_MAX)
		comp[C_B] = RGB_MAX;
	else if(comp[C_B] < RGB_MIN)
		comp[C_B] = RGB_MIN;
}

/*
 * Lighting function that returns 0.0
 * True colour
 */
void LightingColour_Null(br_vector3 *p, br_fvector3 *n, br_active_light *alp,br_scalar *lcomp)
{
   	lcomp[L_R] = lcomp[L_G] = lcomp[L_B] = BR_SCALAR(1.0);
}

/*
 * Lighting for directional light source in model space
 * True colour
 */
void LightingColour_Dirn(br_vector3 *p, br_fvector3 *n, br_active_light *alp,br_scalar *lcomp)
{
	br_scalar c,l,d;

	/*
	 * Accumulate diffuse and specular components
	 *
	 */

	/*
	 * Diffuse (alp->direction already has alp->intensitt factored into it)
	 */
	c = BrFVector3Dot(n,&alp->direction);

	if(c > BR_SCALAR(0.0)) {

		c = BR_MUL(c,fw.material->kd);
		
		lcomp[L_R] = BR_MUL(c,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
		lcomp[L_G] = BR_MUL(c,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
		lcomp[L_B] = BR_MUL(c,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

	    if (fw.material->ks != BR_SCALAR(0.0)) {

			c = BrFVector3Dot(n,&alp->half);

			if(c > SPECULARPOW_CUTOFF) {
				l = BR_MUL(fw.material->ks,alp->intensity);
				d = BR_MULDIV(c,l,fw.material->power-BR_MUL(fw.material->power,c)+c);
				
				lcomp[L_R] += d;
				lcomp[L_G] += d;
				lcomp[L_B] += d;
			}
 		}

		lcomp[L_R] = BR_MUL(lcomp[L_R],BrFixedToScalar(BR_RED(alp->light->colour) << 8));
		lcomp[L_G] = BR_MUL(lcomp[L_G],BrFixedToScalar(BR_GRN(alp->light->colour) << 8));
		lcomp[L_B] = BR_MUL(lcomp[L_B],BrFixedToScalar(BR_BLU(alp->light->colour) << 8));

	} else
		lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
}

/*
 * Lighting for point light source with attenuation
 * True colour
 */
void LightingColour_Point(br_vector3 *p, br_fvector3 *n, br_active_light *alp, br_scalar *lcomp)
{
	br_scalar c,rd,l,d;
	br_vector3 dirn,dirn_norm,r,sn;

	/*
	 * Work out vector between point and light source
	 */
	BrVector3Sub(&dirn,&alp->position,p);
	BrVector3Normalise(&dirn_norm,&dirn);

	/*
	 * Diffuse
	 */

	c = BrFVector3Dot(n,&dirn_norm);

	if(c > BR_SCALAR(0.0)) {

		c = BR_MUL(alp->intensity,BR_MUL(c,fw.material->kd));
		
		lcomp[L_R] = BR_MUL(c,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
		lcomp[L_G] = BR_MUL(c,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
		lcomp[L_B] = BR_MUL(c,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

		if (fw.material->ks != BR_SCALAR(0.0)) {
			/*
			 * Specular
			 */
			BrVector3CopyF(&sn,n);
			rd = BR_CONST_MUL(BrVector3Dot(&dirn_norm,&sn),2);
			BrVector3Scale(&r,&sn,rd);
			BrVector3Sub(&r,&r,&dirn_norm);
		
			c = BrVector3Dot(&fw.eye_l,&r);

			/*
			 * Phong lighting approximation from Gems IV pg. 385
			 */
			if(c > SPECULARPOW_CUTOFF) {
				l = BR_MUL(fw.material->ks,alp->intensity);
				d = BR_MULDIV(c,l,fw.material->power-BR_MUL(fw.material->power,c)+c);
				
				lcomp[L_R] += d;
				lcomp[L_G] += d;
				lcomp[L_B] += d;
			}
		}

		lcomp[L_R] = BR_MUL(lcomp[L_R],BrFixedToScalar(BR_RED(alp->light->colour) << 8));
		lcomp[L_G] = BR_MUL(lcomp[L_G],BrFixedToScalar(BR_GRN(alp->light->colour) << 8));
		lcomp[L_B] = BR_MUL(lcomp[L_B],BrFixedToScalar(BR_BLU(alp->light->colour) << 8));
 	} else 
		lcomp[L_R] = lcomp[L_G] = lcomp[L_B] = BR_SCALAR(0.0);
}

/*
 * Lighting for point light source with attenuation
 * Colour
 */
void LightingColour_PointAttn(br_vector3 *p, br_fvector3 *n, br_active_light *alp, br_scalar *lcomp)
{
	br_scalar c,d,d2,rd,i,power,l;
	br_vector3 dirn,dirn_norm,r,sn;

	/*
	 * Work out vector between point and light source
	 */
	BrVector3Sub(&dirn,&alp->position,p);

	/*
	 * Work out attenuation with distance and distance^2
	 */
	d = BrVector3Length(&dirn);

	if(d == BR_SCALAR(0.0))
	{
    	lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
		return;
	}

	if(d >= BR_SCALAR(180.0))
		d2 = BR_SCALAR(32767.0);
	else
		d2 = BR_MUL(d,d);

	i = alp->light->attenuation_c
		+ BR_MUL(d,alp->light->attenuation_l)
		+ BR_MUL(d2,alp->light->attenuation_q);

	d = BR_RCP(d);

	BrVector3Scale(&dirn_norm,&dirn,d);

	/*
	 * Diffuse
	 */

	c = BrFVector3Dot(n,&dirn_norm);

	if(c > BR_SCALAR(0.0)) {

		c = BR_MUL(alp->intensity,BR_MUL(c,fw.material->kd));
		
		lcomp[L_R] = BR_MUL(c,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
		lcomp[L_G] = BR_MUL(c,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
		lcomp[L_B] = BR_MUL(c,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

		if (fw.material->ks != BR_SCALAR(0.0)) {
			/*
			 * Specular
			 */
			BrVector3CopyF(&sn,n);
			rd = BR_CONST_MUL(BrVector3Dot(&dirn_norm,&sn),2);
			BrVector3Scale(&r,&sn,rd);
			BrVector3Sub(&r,&r,&dirn_norm);
		
			c = BrVector3Dot(&fw.eye_l,&r);

			/*
			 * Phong lighting approximation from Gems IV pg. 385
			 */
			if(c > SPECULARPOW_CUTOFF) {
				l = BR_MUL(fw.material->ks,alp->intensity);
				d = BR_MULDIV(c,l,fw.material->power-BR_MUL(fw.material->power,c)+c);
				
				lcomp[L_R] += d;
				lcomp[L_G] += d;
				lcomp[L_B] += d;
			}
		}

		lcomp[L_R] = BR_MULDIV(lcomp[L_R],BrFixedToScalar(BR_RED(alp->light->colour) << 8),i);
		lcomp[L_G] = BR_MULDIV(lcomp[L_G],BrFixedToScalar(BR_GRN(alp->light->colour) << 8),i);
		lcomp[L_B] = BR_MULDIV(lcomp[L_B],BrFixedToScalar(BR_BLU(alp->light->colour) << 8),i);
 	} else 
		lcomp[L_R] = lcomp[L_G] = lcomp[L_B] = BR_SCALAR(0.0);
}


/*
 * Lighting for spot light source
 * True colour
 */
void LightingColour_Spot(br_vector3 *p, br_fvector3 *n, br_active_light *alp,br_scalar *lcomp)
{
	br_scalar c,rd,i = alp->intensity,power,l,d;
	br_vector3 dirn,dirn_norm,r,sn;

	/*
	 * Work out vector between point and light source
	 */
	BrVector3Sub(&dirn,&alp->position,p);
	BrVector3Normalise(&dirn_norm,&dirn);

	/*
	 * Check cutoff
	 */
	c = BrVector3Dot(&dirn_norm,&alp->direction);
	
	if(c < alp->spot_cosine_outer)
	{
		lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
		return;
	}

	/*
	 * Falloff between inner and outer cones
	 */
	if(c < alp->spot_cosine_inner)
		i = BR_MULDIV(i,alp->spot_cosine_outer - c,
						alp->spot_cosine_outer - alp->spot_cosine_inner);

	/*
	 * Diffuse
	 */

	c = BrFVector3Dot(n,&dirn_norm);

	if(c > BR_SCALAR(0.0)) {

		c = BR_MUL(alp->intensity,BR_MUL(c,fw.material->kd));
		
		lcomp[L_R] = BR_MUL(c,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
		lcomp[L_G] = BR_MUL(c,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
		lcomp[L_B] = BR_MUL(c,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

		if (fw.material->ks != BR_SCALAR(0.0)) {
			/*
			 * Specular
			 */
			BrVector3CopyF(&sn,n);
			rd = BR_CONST_MUL(BrVector3Dot(&dirn_norm,&sn),2);
			BrVector3Scale(&r,&sn,rd);
			BrVector3Sub(&r,&r,&dirn_norm);
		
			c = BrVector3Dot(&fw.eye_l,&r);

			/*
			 * Phong lighting approximation from Gems IV pg. 385
			 */
			if(c > SPECULARPOW_CUTOFF) {
				l = BR_MUL(fw.material->ks,alp->intensity);
				d = BR_MULDIV(c,l,fw.material->power-BR_MUL(fw.material->power,c)+c);
				
				lcomp[L_R] += d;
				lcomp[L_G] += d;
				lcomp[L_B] += d;
			}
		}

		lcomp[L_R] = BR_MUL(lcomp[L_R],BrFixedToScalar(BR_RED(alp->light->colour) << 8));
		lcomp[L_G] = BR_MUL(lcomp[L_G],BrFixedToScalar(BR_GRN(alp->light->colour) << 8));
		lcomp[L_B] = BR_MUL(lcomp[L_B],BrFixedToScalar(BR_BLU(alp->light->colour) << 8));

		lcomp[L_R] = BR_MUL(lcomp[L_R],i);
		lcomp[L_G] = BR_MUL(lcomp[L_G],i);
		lcomp[L_B] = BR_MUL(lcomp[L_B],i);
 	} else 
		lcomp[L_R] = lcomp[L_G] = lcomp[L_B] = BR_SCALAR(0.0);
}

/*
 * Lighting for spot light source with attenuation
 * True colour
 */
void LightingColour_SpotAttn(br_vector3 *p, br_fvector3 *n, br_active_light *alp,br_scalar *lcomp)
{
	br_scalar c,d,d2,rd,i,power,l;
	br_vector3 dirn,dirn_norm,r,sn;

	/*
	 * Work out vector between point and light source
	 */
	BrVector3Sub(&dirn,&alp->position,p);

	d = BrVector3Length(&dirn);

	if(d == BR_SCALAR(0.0))	{
    	lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
		return;
	}

	d2 = BR_RCP(d);
	BrVector3Scale(&dirn_norm,&dirn,d2);

	/*
	 * Check cutoff
	 */
	c = BrVector3Dot(&dirn_norm,&alp->direction);
	
	if(c < alp->spot_cosine_outer)
	{
	    	lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
		return;
	}

	/*
	 * Work out attenuation with distance and distance^2
	 */

	if(d == BR_SCALAR(0.0))
	{
	    	lcomp[L_R]=lcomp[L_G]=lcomp[L_B]=BR_SCALAR(0.0);
	    	return;
	}

	if(d >= BR_SCALAR(180.0))
		d2 = BR_SCALAR(32767.0);
	else
		d2 = BR_MUL(d,d);

	i = alp->light->attenuation_c
		+ BR_MUL(d,alp->light->attenuation_l)
		+ BR_MUL(d2,alp->light->attenuation_q);

	i = BR_RCP(i);

	/*
	 * Falloff between inner and outer cones
	 */
	if(c < alp->spot_cosine_inner)
		i = BR_MULDIV(i,alp->spot_cosine_outer - c,
						alp->spot_cosine_outer - alp->spot_cosine_inner);

	/*
	 * Diffuse
	 */

	c = BrFVector3Dot(n,&dirn_norm);

	if(c > BR_SCALAR(0.0)) {

		c = BR_MUL(alp->intensity,BR_MUL(c,fw.material->kd));
		
		lcomp[L_R] = BR_MUL(c,BrFixedToScalar(BR_RED(fw.material->colour) << 8));
		lcomp[L_G] = BR_MUL(c,BrFixedToScalar(BR_GRN(fw.material->colour) << 8));
		lcomp[L_B] = BR_MUL(c,BrFixedToScalar(BR_BLU(fw.material->colour) << 8));

		if (fw.material->ks != BR_SCALAR(0.0)) {
			/*
			 * Specular
			 */
			BrVector3CopyF(&sn,n);
			rd = BR_CONST_MUL(BrVector3Dot(&dirn_norm,&sn),2);
			BrVector3Scale(&r,&sn,rd);
			BrVector3Sub(&r,&r,&dirn_norm);
		
			c = BrVector3Dot(&fw.eye_l,&r);

			/*
			 * Phong lighting approximation from Gems IV pg. 385
			 */
			if(c > SPECULARPOW_CUTOFF) {
				l = BR_MUL(fw.material->ks,alp->intensity);
				d = BR_MULDIV(c,l,fw.material->power-BR_MUL(fw.material->power,c)+c);
				
				lcomp[L_R] += d;
				lcomp[L_G] += d;
				lcomp[L_B] += d;
			}
		}

		lcomp[L_R] = BR_MUL(lcomp[L_R],BrFixedToScalar(BR_RED(alp->light->colour) << 8));
		lcomp[L_G] = BR_MUL(lcomp[L_G],BrFixedToScalar(BR_GRN(alp->light->colour) << 8));
		lcomp[L_B] = BR_MUL(lcomp[L_B],BrFixedToScalar(BR_BLU(alp->light->colour) << 8));

		lcomp[L_R] = BR_MUL(lcomp[L_R],i);
		lcomp[L_G] = BR_MUL(lcomp[L_G],i);
		lcomp[L_B] = BR_MUL(lcomp[L_B],i);

 	} else 
		lcomp[L_R] = lcomp[L_G] = lcomp[L_B] = BR_SCALAR(0.0);
}