path: root/src/mesa/tnl/t_vb_lighttmp.h

/*
 * Mesa 3-D graphics library
 * Version:  5.1
 *
 * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 *
 * Authors:
 *    Brian Paul
 *    Keith Whitwell <keith@tungstengraphics.com>
 */


#if IDX & LIGHT_TWOSIDE
#  define NR_SIDES 2
#else
#  define NR_SIDES 1
#endif


/* define TRACE to trace lighting code */
/* #define TRACE 1 */

/*
 * ctx is the current context
 * VB is the vertex buffer
 * stage is the lighting stage-private data
 * input is the vector of eye or object-space vertex coordinates
 */
static void TAG(light_rgba_spec)( GLcontext *ctx,
				  struct vertex_buffer *VB,
				  struct tnl_pipeline_stage *stage,
				  GLvector4f *input )
{
   struct light_stage_data *store = LIGHT_STAGE_DATA(stage);
   GLfloat (*base)[3] = ctx->Light._BaseColor;
   GLfloat sumA[2];
   GLuint j;

   const GLuint vstride = input->stride;
   const GLfloat *vertex = (GLfloat *)input->data;
   const GLuint nstride = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->stride;
   const GLfloat *normal = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_NORMAL]->data;

   GLfloat (*Fcolor)[4] = (GLfloat (*)[4]) store->LitColor[0].data;
   GLfloat (*Fspec)[4] = (GLfloat (*)[4]) store->LitSecondary[0].data;
#if IDX & LIGHT_TWOSIDE
   GLfloat (*Bcolor)[4] = (GLfloat (*)[4]) store->LitColor[1].data;
   GLfloat (*Bspec)[4] = (GLfloat (*)[4]) store->LitSecondary[1].data;
#endif

   const GLuint nr = VB->Count;

#ifdef TRACE
   fprintf(stderr, "%s\n", __FUNCTION__ );
#endif

   VB->ColorPtr[0] = &store->LitColor[0];
   VB->SecondaryColorPtr[0] = &store->LitSecondary[0];
   sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];

#if IDX & LIGHT_TWOSIDE
   VB->ColorPtr[1] = &store->LitColor[1];
   VB->SecondaryColorPtr[1] = &store->LitSecondary[1];
   sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif


   store->LitColor[0].stride = 16;
   store->LitColor[1].stride = 16;

   for (j = 0; j < nr; j++,STRIDE_F(vertex,vstride),STRIDE_F(normal,nstride)) {
      GLfloat sum[2][3], spec[2][3];
      struct gl_light *light;

#if IDX & LIGHT_MATERIAL
      update_materials( ctx, store );
      sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];
#if IDX & LIGHT_TWOSIDE
      sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif
#endif

      COPY_3V(sum[0], base[0]);
      ZERO_3V(spec[0]);

#if IDX & LIGHT_TWOSIDE
      COPY_3V(sum[1], base[1]);
      ZERO_3V(spec[1]);
#endif

      /* Add contribution from each enabled light source */
      foreach (light, &ctx->Light.EnabledList) {
	 GLfloat n_dot_h;
	 GLfloat correction;
	 GLint side;
	 GLfloat contrib[3];
	 GLfloat attenuation;
	 GLfloat VP[3];  /* unit vector from vertex to light */
	 GLfloat n_dot_VP;       /* n dot VP */
	 GLfloat *h;

	 /* compute VP and attenuation */
	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
	    /* directional light */
	    COPY_3V(VP, light->_VP_inf_norm);
	    attenuation = light->_VP_inf_spot_attenuation;
	 }
	 else {
	    GLfloat d;     /* distance from vertex to light */

	    SUB_3V(VP, light->_Position, vertex);

	    d = (GLfloat) LEN_3FV( VP );

	    if (d > 1e-6) {
	       GLfloat invd = 1.0F / d;
	       SELF_SCALE_SCALAR_3V(VP, invd);
	    }

	    attenuation = 1.0F / (light->ConstantAttenuation + d *
				  (light->LinearAttenuation + d *
				   light->QuadraticAttenuation));

	    /* spotlight attenuation */
	    if (light->_Flags & LIGHT_SPOT) {
	       GLfloat PV_dot_dir = - DOT3(VP, light->_NormSpotDirection);

	       if (PV_dot_dir<light->_CosCutoff) {
		  continue; /* this light makes no contribution */
	       }
	       else {
		  GLdouble x = PV_dot_dir * (EXP_TABLE_SIZE-1);
		  GLint k = (GLint) x;
		  GLfloat spot = (GLfloat) (light->_SpotExpTable[k][0]
				    + (x-k)*light->_SpotExpTable[k][1]);
		  attenuation *= spot;
	       }
	    }
	 }

	 if (attenuation < 1e-3)
	    continue;		/* this light makes no contribution */

	 /* Compute dot product or normal and vector from V to light pos */
	 n_dot_VP = DOT3( normal, VP );

	 /* Which side gets the diffuse & specular terms? */
	 if (n_dot_VP < 0.0F) {
	    ACC_SCALE_SCALAR_3V(sum[0], attenuation, light->_MatAmbient[0]);
#if IDX & LIGHT_TWOSIDE
	    side = 1;
	    correction = -1;
	    n_dot_VP = -n_dot_VP;
#else
            continue;
#endif
	 }
         else {
#if IDX & LIGHT_TWOSIDE
            ACC_SCALE_SCALAR_3V( sum[1], attenuation, light->_MatAmbient[1]);
#endif
	    side = 0;
	    correction = 1;
	 }

	 /* diffuse term */
	 COPY_3V(contrib, light->_MatAmbient[side]);
	 ACC_SCALE_SCALAR_3V(contrib, n_dot_VP, light->_MatDiffuse[side]);
	 ACC_SCALE_SCALAR_3V(sum[side], attenuation, contrib );

	 /* specular term - cannibalize VP... */
	 if (ctx->Light.Model.LocalViewer) {
	    GLfloat v[3];
	    COPY_3V(v, vertex);
	    NORMALIZE_3FV(v);
	    SUB_3V(VP, VP, v);                /* h = VP + VPe */
	    h = VP;
	    NORMALIZE_3FV(h);
	 }
	 else if (light->_Flags & LIGHT_POSITIONAL) {
	    h = VP;
	    ACC_3V(h, ctx->_EyeZDir);
	    NORMALIZE_3FV(h);
	 }
         else {
	    h = light->_h_inf_norm;
	 }

	 n_dot_h = correction * DOT3(normal, h);

	 if (n_dot_h > 0.0F) {
	    GLfloat spec_coef;
	    struct gl_shine_tab *tab = ctx->_ShineTable[side];
	    GET_SHINE_TAB_ENTRY( tab, n_dot_h, spec_coef );

	    if (spec_coef > 1.0e-10) {
	       spec_coef *= attenuation;
	       ACC_SCALE_SCALAR_3V( spec[side], spec_coef,
				    light->_MatSpecular[side]);
	    }
	 }
      } /*loop over lights*/

      COPY_3V( Fcolor[j], sum[0] );
      COPY_3V( Fspec[j], spec[0] );
      Fcolor[j][3] = sumA[0];

#if IDX & LIGHT_TWOSIDE
      COPY_3V( Bcolor[j], sum[1] );
      COPY_3V( Bspec[j], spec[1] );
      Bcolor[j][3] = sumA[1];
#endif
   }
}


static void TAG(light_rgba)( GLcontext *ctx,
			     struct vertex_buffer *VB,
			     struct tnl_pipeline_stage *stage,
			     GLvector4f *input )
{
   struct light_stage_data *store = LIGHT_STAGE_DATA(stage);
   GLuint j;

   GLfloat (*base)[3] = ctx->Light._BaseColor;
   GLfloat sumA[2];

   const GLuint vstride = input->stride;
   const GLfloat *vertex = (GLfloat *) input->data;
   const GLuint nstride = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->stride;
   const GLfloat *normal = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_NORMAL]->data;

   GLfloat (*Fcolor)[4] = (GLfloat (*)[4]) store->LitColor[0].data;
#if IDX & LIGHT_TWOSIDE
   GLfloat (*Bcolor)[4] = (GLfloat (*)[4]) store->LitColor[1].data;
#endif

   const GLuint nr = VB->Count;

#ifdef TRACE
   fprintf(stderr, "%s\n", __FUNCTION__ );
#endif

   VB->ColorPtr[0] = &store->LitColor[0];
   sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];

#if IDX & LIGHT_TWOSIDE
   VB->ColorPtr[1] = &store->LitColor[1];
   sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif

   store->LitColor[0].stride = 16;
   store->LitColor[1].stride = 16;

   for (j = 0; j < nr; j++,STRIDE_F(vertex,vstride),STRIDE_F(normal,nstride)) {
      GLfloat sum[2][3];
      struct gl_light *light;

#if IDX & LIGHT_MATERIAL
      update_materials( ctx, store );
      sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];
#if IDX & LIGHT_TWOSIDE
      sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif
#endif

      COPY_3V(sum[0], base[0]);

#if IDX & LIGHT_TWOSIDE
      COPY_3V(sum[1], base[1]);
#endif

      /* Add contribution from each enabled light source */
      foreach (light, &ctx->Light.EnabledList) {

	 GLfloat n_dot_h;
	 GLfloat correction;
	 GLint side;
	 GLfloat contrib[3];
	 GLfloat attenuation = 1.0;
	 GLfloat VP[3];          /* unit vector from vertex to light */
	 GLfloat n_dot_VP;       /* n dot VP */
	 GLfloat *h;

	 /* compute VP and attenuation */
	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
	    /* directional light */
	    COPY_3V(VP, light->_VP_inf_norm);
	    attenuation = light->_VP_inf_spot_attenuation;
	 }
	 else {
	    GLfloat d;     /* distance from vertex to light */


	    SUB_3V(VP, light->_Position, vertex);

	    d = (GLfloat) LEN_3FV( VP );

	    if ( d > 1e-6) {
	       GLfloat invd = 1.0F / d;
	       SELF_SCALE_SCALAR_3V(VP, invd);
	    }

            attenuation = 1.0F / (light->ConstantAttenuation + d *
                                  (light->LinearAttenuation + d *
                                   light->QuadraticAttenuation));

	    /* spotlight attenuation */
	    if (light->_Flags & LIGHT_SPOT) {
	       GLfloat PV_dot_dir = - DOT3(VP, light->_NormSpotDirection);

	       if (PV_dot_dir<light->_CosCutoff) {
		  continue; /* this light makes no contribution */
	       }
	       else {
		  GLdouble x = PV_dot_dir * (EXP_TABLE_SIZE-1);
		  GLint k = (GLint) x;
		  GLfloat spot = (GLfloat) (light->_SpotExpTable[k][0]
				  + (x-k)*light->_SpotExpTable[k][1]);
		  attenuation *= spot;
	       }
	    }
	 }

	 if (attenuation < 1e-3)
	    continue;		/* this light makes no contribution */

	 /* Compute dot product or normal and vector from V to light pos */
	 n_dot_VP = DOT3( normal, VP );

	 /* which side are we lighting? */
	 if (n_dot_VP < 0.0F) {
	    ACC_SCALE_SCALAR_3V(sum[0], attenuation, light->_MatAmbient[0]);
#if IDX & LIGHT_TWOSIDE
	    side = 1;
	    correction = -1;
	    n_dot_VP = -n_dot_VP;
#else
            continue;
#endif
	 }
         else {
#if IDX & LIGHT_TWOSIDE
            ACC_SCALE_SCALAR_3V( sum[1], attenuation, light->_MatAmbient[1]);
#endif
	    side = 0;
	    correction = 1;
	 }

	 COPY_3V(contrib, light->_MatAmbient[side]);

	 /* diffuse term */
	 ACC_SCALE_SCALAR_3V(contrib, n_dot_VP, light->_MatDiffuse[side]);

	 /* specular term - cannibalize VP... */
	 {
	    if (ctx->Light.Model.LocalViewer) {
	       GLfloat v[3];
	       COPY_3V(v, vertex);
	       NORMALIZE_3FV(v);
	       SUB_3V(VP, VP, v);                /* h = VP + VPe */
	       h = VP;
	       NORMALIZE_3FV(h);
	    }
	    else if (light->_Flags & LIGHT_POSITIONAL) {
	       h = VP;
	       ACC_3V(h, ctx->_EyeZDir);
	       NORMALIZE_3FV(h);
	    }
            else {
	       h = light->_h_inf_norm;
	    }

	    n_dot_h = correction * DOT3(normal, h);

	    if (n_dot_h > 0.0F)
	    {
	       GLfloat spec_coef;
	       struct gl_shine_tab *tab = ctx->_ShineTable[side];

	       GET_SHINE_TAB_ENTRY( tab, n_dot_h, spec_coef );

	       ACC_SCALE_SCALAR_3V( contrib, spec_coef,
				    light->_MatSpecular[side]);
	    }
	 }

	 ACC_SCALE_SCALAR_3V( sum[side], attenuation, contrib );
      }

      COPY_3V( Fcolor[j], sum[0] );
      Fcolor[j][3] = sumA[0];

#if IDX & LIGHT_TWOSIDE
      COPY_3V( Bcolor[j], sum[1] );
      Bcolor[j][3] = sumA[1];
#endif
   }
}




/* As below, but with just a single light.
 */
static void TAG(light_fast_rgba_single)( GLcontext *ctx,
					 struct vertex_buffer *VB,
					 struct tnl_pipeline_stage *stage,
					 GLvector4f *input )

{
   struct light_stage_data *store = LIGHT_STAGE_DATA(stage);
   const GLuint nstride = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->stride;
   const GLfloat *normal = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_NORMAL]->data;
   GLfloat (*Fcolor)[4] = (GLfloat (*)[4]) store->LitColor[0].data;
#if IDX & LIGHT_TWOSIDE
   GLfloat (*Bcolor)[4] = (GLfloat (*)[4]) store->LitColor[1].data;
#endif
   const struct gl_light *light = ctx->Light.EnabledList.next;
   GLuint j = 0;
   GLfloat base[2][4];
#if IDX & LIGHT_MATERIAL
   const GLuint nr = VB->Count;
#else
   const GLuint nr = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->count;
#endif

#ifdef TRACE
   fprintf(stderr, "%s\n", __FUNCTION__ );
#endif

   (void) input;		/* doesn't refer to Eye or Obj */

   VB->ColorPtr[0] = &store->LitColor[0];
#if IDX & LIGHT_TWOSIDE
   VB->ColorPtr[1] = &store->LitColor[1];
#endif

   if (nr > 1) {
      store->LitColor[0].stride = 16;
      store->LitColor[1].stride = 16;
   }
   else {
      store->LitColor[0].stride = 0;
      store->LitColor[1].stride = 0;
   }

   for (j = 0; j < nr; j++, STRIDE_F(normal,nstride)) {

      GLfloat n_dot_VP;

#if IDX & LIGHT_MATERIAL
      update_materials( ctx, store );
#endif

      /* No attenuation, so incoporate _MatAmbient into base color.
       */
#if !(IDX & LIGHT_MATERIAL)
      if ( j == 0 )
#endif
      {
	 COPY_3V(base[0], light->_MatAmbient[0]);
	 ACC_3V(base[0], ctx->Light._BaseColor[0] );
	 base[0][3] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];

#if IDX & LIGHT_TWOSIDE
         COPY_3V(base[1], light->_MatAmbient[1]);
         ACC_3V(base[1], ctx->Light._BaseColor[1]);
         base[1][3] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif
      }

      n_dot_VP = DOT3(normal, light->_VP_inf_norm);

      if (n_dot_VP < 0.0F) {
#if IDX & LIGHT_TWOSIDE
         GLfloat n_dot_h = -DOT3(normal, light->_h_inf_norm);
         GLfloat sum[3];
         COPY_3V(sum, base[1]);
         ACC_SCALE_SCALAR_3V(sum, -n_dot_VP, light->_MatDiffuse[1]);
         if (n_dot_h > 0.0F) {
            GLfloat spec;
            GET_SHINE_TAB_ENTRY( ctx->_ShineTable[1], n_dot_h, spec );
            ACC_SCALE_SCALAR_3V(sum, spec, light->_MatSpecular[1]);
         }
         COPY_3V(Bcolor[j], sum );
         Bcolor[j][3] = base[1][3];
#endif
	 COPY_4FV(Fcolor[j], base[0]);
      }
      else {
	 GLfloat n_dot_h = DOT3(normal, light->_h_inf_norm);
	 GLfloat sum[3];
	 COPY_3V(sum, base[0]);
	 ACC_SCALE_SCALAR_3V(sum, n_dot_VP, light->_MatDiffuse[0]);
	 if (n_dot_h > 0.0F) {
	    GLfloat spec;
	    GET_SHINE_TAB_ENTRY( ctx->_ShineTable[0], n_dot_h, spec );
	    ACC_SCALE_SCALAR_3V(sum, spec, light->_MatSpecular[0]);

	 }
	 COPY_3V(Fcolor[j], sum );
	 Fcolor[j][3] = base[0][3];
#if IDX & LIGHT_TWOSIDE
         COPY_4FV(Bcolor[j], base[1]);
#endif
      }
   }
}


/* Light infinite lights
 */
static void TAG(light_fast_rgba)( GLcontext *ctx,
				  struct vertex_buffer *VB,
				  struct tnl_pipeline_stage *stage,
				  GLvector4f *input )
{
   struct light_stage_data *store = LIGHT_STAGE_DATA(stage);
   GLfloat sumA[2];
   const GLuint nstride = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->stride;
   const GLfloat *normal = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_NORMAL]->data;
   GLfloat (*Fcolor)[4] = (GLfloat (*)[4]) store->LitColor[0].data;
#if IDX & LIGHT_TWOSIDE
   GLfloat (*Bcolor)[4] = (GLfloat (*)[4]) store->LitColor[1].data;
#endif
   GLuint j = 0;
#if IDX & LIGHT_MATERIAL
   const GLuint nr = VB->Count;
#else
   const GLuint nr = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->count;
#endif
   const struct gl_light *light;

#ifdef TRACE
   fprintf(stderr, "%s %d\n", __FUNCTION__, nr );
#endif

   (void) input;

   sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];
   sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];

   VB->ColorPtr[0] = &store->LitColor[0];
#if IDX & LIGHT_TWOSIDE
   VB->ColorPtr[1] = &store->LitColor[1];
#endif

   if (nr > 1) {
      store->LitColor[0].stride = 16;
      store->LitColor[1].stride = 16;
   }
   else {
      store->LitColor[0].stride = 0;
      store->LitColor[1].stride = 0;
   }

   for (j = 0; j < nr; j++, STRIDE_F(normal,nstride)) {

      GLfloat sum[2][3];

#if IDX & LIGHT_MATERIAL
      update_materials( ctx, store );

      sumA[0] = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_DIFFUSE][3];
#if IDX & LIGHT_TWOSIDE
      sumA[1] = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_DIFFUSE][3];
#endif
#endif


      COPY_3V(sum[0], ctx->Light._BaseColor[0]);
#if IDX & LIGHT_TWOSIDE
      COPY_3V(sum[1], ctx->Light._BaseColor[1]);
#endif

      foreach (light, &ctx->Light.EnabledList) {
	 GLfloat n_dot_h, n_dot_VP, spec;

	 ACC_3V(sum[0], light->_MatAmbient[0]);
#if IDX & LIGHT_TWOSIDE
         ACC_3V(sum[1], light->_MatAmbient[1]);
#endif

	 n_dot_VP = DOT3(normal, light->_VP_inf_norm);

	 if (n_dot_VP > 0.0F) {
	    ACC_SCALE_SCALAR_3V(sum[0], n_dot_VP, light->_MatDiffuse[0]);
	    n_dot_h = DOT3(normal, light->_h_inf_norm);
	    if (n_dot_h > 0.0F) {
	       struct gl_shine_tab *tab = ctx->_ShineTable[0];
	       GET_SHINE_TAB_ENTRY( tab, n_dot_h, spec );
	       ACC_SCALE_SCALAR_3V( sum[0], spec, light->_MatSpecular[0]);
	    }
	 }
#if IDX & LIGHT_TWOSIDE
         else {
	    ACC_SCALE_SCALAR_3V(sum[1], -n_dot_VP, light->_MatDiffuse[1]);
	    n_dot_h = -DOT3(normal, light->_h_inf_norm);
	    if (n_dot_h > 0.0F) {
	       struct gl_shine_tab *tab = ctx->_ShineTable[1];
	       GET_SHINE_TAB_ENTRY( tab, n_dot_h, spec );
	       ACC_SCALE_SCALAR_3V( sum[1], spec, light->_MatSpecular[1]);
	    }
	 }
#endif
      }

      COPY_3V( Fcolor[j], sum[0] );
      Fcolor[j][3] = sumA[0];

#if IDX & LIGHT_TWOSIDE
      COPY_3V( Bcolor[j], sum[1] );
      Bcolor[j][3] = sumA[1];
#endif
   }
}





/*
 * Use current lighting/material settings to compute the color indexes
 * for an array of vertices.
 * Input:  n - number of vertices to light
 *         side - 0=use front material, 1=use back material
 *         vertex - array of [n] vertex position in eye coordinates
 *         normal - array of [n] surface normal vector
 * Output:  indexResult - resulting array of [n] color indexes
 */
static void TAG(light_ci)( GLcontext *ctx,
			   struct vertex_buffer *VB,
			   struct tnl_pipeline_stage *stage,
			   GLvector4f *input )
{
   struct light_stage_data *store = LIGHT_STAGE_DATA(stage);
   GLuint j;
   const GLuint vstride = input->stride;
   const GLfloat *vertex = (GLfloat *) input->data;
   const GLuint nstride = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->stride;
   const GLfloat *normal = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_NORMAL]->data;
   GLfloat *indexResult[2];
   const GLuint nr = VB->Count;

#ifdef TRACE
   fprintf(stderr, "%s\n", __FUNCTION__ );
#endif

   VB->AttribPtr[_TNL_ATTRIB_COLOR_INDEX] = &store->LitIndex[0];
#if IDX & LIGHT_TWOSIDE
   VB->BackfaceIndexPtr = &store->LitIndex[1];
#endif

   indexResult[0] = (GLfloat *)VB->AttribPtr[_TNL_ATTRIB_COLOR_INDEX]->data;
#if IDX & LIGHT_TWOSIDE
   indexResult[1] = (GLfloat *)VB->BackfaceIndexPtr->data;
#endif

   /* loop over vertices */
   for (j=0; j<nr; j++,STRIDE_F(vertex,vstride),STRIDE_F(normal, nstride)) {
      GLfloat diffuse[2], specular[2];
      GLuint side = 0;
      struct gl_light *light;

#if IDX & LIGHT_MATERIAL
      update_materials( ctx, store );
#endif

      diffuse[0] = specular[0] = 0.0F;

#if IDX & LIGHT_TWOSIDE
	 diffuse[1] = specular[1] = 0.0F;
#endif

      /* Accumulate diffuse and specular from each light source */
      foreach (light, &ctx->Light.EnabledList) {

	 GLfloat attenuation = 1.0F;
	 GLfloat VP[3];  /* unit vector from vertex to light */
	 GLfloat n_dot_VP;  /* dot product of l and n */
	 GLfloat *h, n_dot_h, correction = 1.0;

	 /* compute l and attenuation */
	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
	    /* directional light */
	    COPY_3V(VP, light->_VP_inf_norm);
	 }
	 else {
	    GLfloat d;     /* distance from vertex to light */

	    SUB_3V(VP, light->_Position, vertex);

	    d = (GLfloat) LEN_3FV( VP );
	    if ( d > 1e-6) {
	       GLfloat invd = 1.0F / d;
	       SELF_SCALE_SCALAR_3V(VP, invd);
	    }

	    attenuation = 1.0F / (light->ConstantAttenuation + d *
				  (light->LinearAttenuation + d *
				   light->QuadraticAttenuation));

	    /* spotlight attenuation */
	    if (light->_Flags & LIGHT_SPOT) {
	       GLfloat PV_dot_dir = - DOT3(VP, light->_NormSpotDirection);
	       if (PV_dot_dir < light->_CosCutoff) {
		  continue; /* this light makes no contribution */
	       }
	       else {
		  GLdouble x = PV_dot_dir * (EXP_TABLE_SIZE-1);
		  GLint k = (GLint) x;
		  GLfloat spot = (GLfloat) (light->_SpotExpTable[k][0]
				  + (x-k)*light->_SpotExpTable[k][1]);
		  attenuation *= spot;
	       }
	    }
	 }

	 if (attenuation < 1e-3)
	    continue;		/* this light makes no contribution */

	 n_dot_VP = DOT3( normal, VP );

	 /* which side are we lighting? */
	 if (n_dot_VP < 0.0F) {
#if IDX & LIGHT_TWOSIDE
	    side = 1;
	    correction = -1;
	    n_dot_VP = -n_dot_VP;
#else
            continue;
#endif
	 }

	 /* accumulate diffuse term */
	 diffuse[side] += n_dot_VP * light->_dli * attenuation;

	 /* specular term */
	 if (ctx->Light.Model.LocalViewer) {
	    GLfloat v[3];
	    COPY_3V(v, vertex);
	    NORMALIZE_3FV(v);
	    SUB_3V(VP, VP, v);                /* h = VP + VPe */
	    h = VP;
	    NORMALIZE_3FV(h);
	 }
	 else if (light->_Flags & LIGHT_POSITIONAL) {
	    h = VP;
            /* Strangely, disabling this addition fixes a conformance
             * problem.  If this code is enabled, l_sed.c fails.
             */
	    /*ACC_3V(h, ctx->_EyeZDir);*/
	    NORMALIZE_3FV(h);
	 }
         else {
	    h = light->_h_inf_norm;
	 }

	 n_dot_h = correction * DOT3(normal, h);
	 if (n_dot_h > 0.0F) {
	    GLfloat spec_coef;
	    struct gl_shine_tab *tab = ctx->_ShineTable[side];
	    GET_SHINE_TAB_ENTRY( tab, n_dot_h, spec_coef);
	    specular[side] += spec_coef * light->_sli * attenuation;
	 }
      } /*loop over lights*/

      /* Now compute final color index */
      for (side = 0 ; side < NR_SIDES ; side++) {
	 const GLfloat *ind = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_INDEXES + side];
	 GLfloat index;

	 if (specular[side] > 1.0F) {
	    index = ind[MAT_INDEX_SPECULAR];
	 }
	 else {
	    GLfloat d_a = ind[MAT_INDEX_DIFFUSE] - ind[MAT_INDEX_AMBIENT];
	    GLfloat s_a = ind[MAT_INDEX_SPECULAR] - ind[MAT_INDEX_AMBIENT];
	    index = (ind[MAT_INDEX_AMBIENT]
		     + diffuse[side] * (1.0F-specular[side]) * d_a
		     + specular[side] * s_a);
	    if (index > ind[MAT_INDEX_SPECULAR]) {
	       index = ind[MAT_INDEX_SPECULAR];
	    }
	 }
	 indexResult[side][j] = index;
      }
   } /*for vertex*/
}



static void TAG(init_light_tab)( void )
{
   _tnl_light_tab[IDX] = TAG(light_rgba);
   _tnl_light_fast_tab[IDX] = TAG(light_fast_rgba);
   _tnl_light_fast_single_tab[IDX] = TAG(light_fast_rgba_single);
   _tnl_light_spec_tab[IDX] = TAG(light_rgba_spec);
   _tnl_light_ci_tab[IDX] = TAG(light_ci);
}


#undef TAG
#undef IDX
#undef NR_SIDES