light.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

 * lighting, and the cost of doing it early may be partially offset
 * by keeping a MRU cache of shine tables for various shine values.
 */
void
_mesa_invalidate_shine_table( GLcontext *ctx, GLuint side )
{
   ASSERT(side < 2);
   if (ctx->_ShineTable[side])
      ctx->_ShineTable[side]->refcount--;
   ctx->_ShineTable[side] = NULL;
}


static void
validate_shine_table( GLcontext *ctx, GLuint side, GLfloat shininess )
{
   struct gl_shine_tab *list = ctx->_ShineTabList;
   struct gl_shine_tab *s;

   ASSERT(side < 2);

   foreach(s, list)
      if ( s->shininess == shininess )
	 break;

   if (s == list) {
      GLint j;
      GLfloat *m;

      foreach(s, list)
	 if (s->refcount == 0)
	    break;

      m = s->tab;
      m[0] = 0.0;
      if (shininess == 0.0) {
	 for (j = 1 ; j <= SHINE_TABLE_SIZE ; j++)
	    m[j] = 1.0;
      }
      else {
	 for (j = 1 ; j < SHINE_TABLE_SIZE ; j++) {
            GLdouble t, x = j / (GLfloat) (SHINE_TABLE_SIZE - 1);
            if (x < 0.005) /* underflow check */
               x = 0.005;
            t = _mesa_pow(x, shininess);
	    if (t > 1e-20)
	       m[j] = (GLfloat) t;
	    else
	       m[j] = 0.0;
	 }
	 m[SHINE_TABLE_SIZE] = 1.0;
      }

      s->shininess = shininess;
   }

   if (ctx->_ShineTable[side])
      ctx->_ShineTable[side]->refcount--;

   ctx->_ShineTable[side] = s;
   move_to_tail( list, s );
   s->refcount++;
}


void
_mesa_validate_all_lighting_tables( GLcontext *ctx )
{
   GLuint i;
   GLfloat shininess;
   
   shininess = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_SHININESS][0];
   if (!ctx->_ShineTable[0] || ctx->_ShineTable[0]->shininess != shininess)
      validate_shine_table( ctx, 0, shininess );

   shininess = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_SHININESS][0];
   if (!ctx->_ShineTable[1] || ctx->_ShineTable[1]->shininess != shininess)
      validate_shine_table( ctx, 1, shininess );

   for (i = 0; i < ctx->Const.MaxLights; i++)
      if (ctx->Light.Light[i]._SpotExpTable[0][0] == -1)
	 validate_spot_exp_table( &ctx->Light.Light[i] );
}


/**
 * Examine current lighting parameters to determine if the optimized lighting
 * function can be used.
 * Also, precompute some lighting values such as the products of light
 * source and material ambient, diffuse and specular coefficients.
 */
void
_mesa_update_lighting( GLcontext *ctx )
{
   struct gl_light *light;
   ctx->Light._NeedEyeCoords = GL_FALSE;
   ctx->Light._Flags = 0;

   if (!ctx->Light.Enabled)
      return;

   foreach(light, &ctx->Light.EnabledList) {
      ctx->Light._Flags |= light->_Flags;
   }

   ctx->Light._NeedVertices =
      ((ctx->Light._Flags & (LIGHT_POSITIONAL|LIGHT_SPOT)) ||
       ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR ||
       ctx->Light.Model.LocalViewer);

   ctx->Light._NeedEyeCoords = ((ctx->Light._Flags & LIGHT_POSITIONAL) ||
				ctx->Light.Model.LocalViewer);

   /* XXX: This test is overkill & needs to be fixed both for software and
    * hardware t&l drivers.  The above should be sufficient & should
    * be tested to verify this.
    */
   if (ctx->Light._NeedVertices)
      ctx->Light._NeedEyeCoords = GL_TRUE;

   /* Precompute some shading values.  Although we reference
    * Light.Material here, we can get away without flushing
    * FLUSH_UPDATE_CURRENT, as when any outstanding material changes
    * are flushed, they will update the derived state at that time.
    */
   if (ctx->Visual.rgbMode) {
      if (ctx->Light.Model.TwoSide)
	 _mesa_update_material( ctx, 
				MAT_BIT_FRONT_EMISSION |
				MAT_BIT_FRONT_AMBIENT |
				MAT_BIT_FRONT_DIFFUSE | 
				MAT_BIT_FRONT_SPECULAR |
				MAT_BIT_BACK_EMISSION |
				MAT_BIT_BACK_AMBIENT |
				MAT_BIT_BACK_DIFFUSE | 
				MAT_BIT_BACK_SPECULAR);
      else
	 _mesa_update_material( ctx, 
				MAT_BIT_FRONT_EMISSION |
				MAT_BIT_FRONT_AMBIENT |
				MAT_BIT_FRONT_DIFFUSE | 
				MAT_BIT_FRONT_SPECULAR);
   }
   else {
      static const GLfloat ci[3] = { .30F, .59F, .11F };
      foreach(light, &ctx->Light.EnabledList) {
	 light->_dli = DOT3(ci, light->Diffuse);
	 light->_sli = DOT3(ci, light->Specular);
      }
   }
}


/**
 * Update state derived from light position, spot direction.
 * Called upon:
 *   _NEW_MODELVIEW
 *   _NEW_LIGHT
 *   _TNL_NEW_NEED_EYE_COORDS
 *
 * Update on (_NEW_MODELVIEW | _NEW_LIGHT) when lighting is enabled.
 * Also update on lighting space changes.
 */
static void
compute_light_positions( GLcontext *ctx )
{
   struct gl_light *light;
   static const GLfloat eye_z[3] = { 0, 0, 1 };

   if (!ctx->Light.Enabled)
      return;

   if (ctx->_NeedEyeCoords) {
      COPY_3V( ctx->_EyeZDir, eye_z );
   }
   else {
      TRANSFORM_NORMAL( ctx->_EyeZDir, eye_z, ctx->ModelviewMatrixStack.Top->m );
   }

   foreach (light, &ctx->Light.EnabledList) {

      if (ctx->_NeedEyeCoords) {
         /* _Position is in eye coordinate space */
	 COPY_4FV( light->_Position, light->EyePosition );
      }
      else {
         /* _Position is in object coordinate space */
	 TRANSFORM_POINT( light->_Position, ctx->ModelviewMatrixStack.Top->inv,
			  light->EyePosition );
      }

      if (!(light->_Flags & LIGHT_POSITIONAL)) {
	 /* VP (VP) = Normalize( Position ) */
	 COPY_3V( light->_VP_inf_norm, light->_Position );
	 NORMALIZE_3FV( light->_VP_inf_norm );

	 if (!ctx->Light.Model.LocalViewer) {
	    /* _h_inf_norm = Normalize( V_to_P + <0,0,1> ) */
	    ADD_3V( light->_h_inf_norm, light->_VP_inf_norm, ctx->_EyeZDir);
	    NORMALIZE_3FV( light->_h_inf_norm );
	 }
	 light->_VP_inf_spot_attenuation = 1.0;
      }
      else {
         /* positional light w/ homogeneous coordinate, divide by W */
         GLfloat wInv = 1.0 / light->_Position[3];
         light->_Position[0] *= wInv;
         light->_Position[1] *= wInv;
         light->_Position[2] *= wInv;
      }

      if (light->_Flags & LIGHT_SPOT) {
	 if (ctx->_NeedEyeCoords) {
	    COPY_3V( light->_NormDirection, light->EyeDirection );
	 }
         else {
	    TRANSFORM_NORMAL( light->_NormDirection,
			      light->EyeDirection,
			      ctx->ModelviewMatrixStack.Top->m);
	 }

	 NORMALIZE_3FV( light->_NormDirection );

	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
	    GLfloat PV_dot_dir = - DOT3(light->_VP_inf_norm,
					light->_NormDirection);

	    if (PV_dot_dir > light->_CosCutoff) {
	       double x = PV_dot_dir * (EXP_TABLE_SIZE-1);
	       int k = (int) x;
	       light->_VP_inf_spot_attenuation =
		  (GLfloat) (light->_SpotExpTable[k][0] +
		   (x-k)*light->_SpotExpTable[k][1]);
	    }
	    else {
	       light->_VP_inf_spot_attenuation = 0;
            }
	 }
      }
   }
}



static void
update_modelview_scale( GLcontext *ctx )
{
   ctx->_ModelViewInvScale = 1.0F;
   if (!_math_matrix_is_length_preserving(ctx->ModelviewMatrixStack.Top)) {
      const GLfloat *m = ctx->ModelviewMatrixStack.Top->inv;
      GLfloat f = m[2] * m[2] + m[6] * m[6] + m[10] * m[10];
      if (f < 1e-12) f = 1.0;
      if (ctx->_NeedEyeCoords)
	 ctx->_ModelViewInvScale = (GLfloat) INV_SQRTF(f);
      else
	 ctx->_ModelViewInvScale = (GLfloat) SQRTF(f);
   }
}


/**
 * Bring up to date any state that relies on _NeedEyeCoords.
 */
void
_mesa_update_tnl_spaces( GLcontext *ctx, GLuint new_state )
{
   const GLuint oldneedeyecoords = ctx->_NeedEyeCoords;

   (void) new_state;
   ctx->_NeedEyeCoords = GL_FALSE;

   if (ctx->_ForceEyeCoords ||
       (ctx->Texture._GenFlags & TEXGEN_NEED_EYE_COORD) ||
       ctx->Point._Attenuated ||
       ctx->Light._NeedEyeCoords)
      ctx->_NeedEyeCoords = GL_TRUE;

   if (ctx->Light.Enabled &&
       !_math_matrix_is_length_preserving(ctx->ModelviewMatrixStack.Top))
      ctx->_NeedEyeCoords = GL_TRUE;

   /* Check if the truth-value interpretations of the bitfields have
    * changed:
    */
   if (oldneedeyecoords != ctx->_NeedEyeCoords) {
      /* Recalculate all state that depends on _NeedEyeCoords.
       */
      update_modelview_scale(ctx);
      compute_light_positions( ctx );

      if (ctx->Driver.LightingSpaceChange)
	 ctx->Driver.LightingSpaceChange( ctx );
   }
   else {
      GLuint new_state = ctx->NewState;

      /* Recalculate that same state only if it has been invalidated
       * by other statechanges.
       */
      if (new_state & _NEW_MODELVIEW)
	 update_modelview_scale(ctx);

      if (new_state & (_NEW_LIGHT|_NEW_MODELVIEW))
	 compute_light_positions( ctx );
   }
}


/**
 * Drivers may need this if the hardware tnl unit doesn't support the
 * light-in-modelspace optimization.  It's also useful for debugging.
 */
void
_mesa_allow_light_in_model( GLcontext *ctx, GLboolean flag )
{
   ctx->_ForceEyeCoords = !flag;
   ctx->NewState |= _NEW_POINT;	/* one of the bits from
				 * _MESA_NEW_NEED_EYE_COORDS.
				 */
}



/**********************************************************************/
/*****                      Initialization                        *****/
/**********************************************************************/

/**
 * Initialize the n-th light data structure.
 *
 * \param l pointer to the gl_light structure to be initialized.
 * \param n number of the light. 
 * \note The defaults for light 0 are different than the other lights.
 */
static void
init_light( struct gl_light *l, GLuint n )
{
   make_empty_list( l );

   ASSIGN_4V( l->Ambient, 0.0, 0.0, 0.0, 1.0 );
   if (n==0) {
      ASSIGN_4V( l->Diffuse, 1.0, 1.0, 1.0, 1.0 );
      ASSIGN_4V( l->Specular, 1.0, 1.0, 1.0, 1.0 );
   }
   else {
      ASSIGN_4V( l->Diffuse, 0.0, 0.0, 0.0, 1.0 );
      ASSIGN_4V( l->Specular, 0.0, 0.0, 0.0, 1.0 );
   }
   ASSIGN_4V( l->EyePosition, 0.0, 0.0, 1.0, 0.0 );
   ASSIGN_3V( l->EyeDirection, 0.0, 0.0, -1.0 );
   l->SpotExponent = 0.0;
   _mesa_invalidate_spot_exp_table( l );
   l->SpotCutoff = 180.0;
   l->_CosCutoffNeg = -1.0f;
   l->_CosCutoff = 0.0;		/* KW: -ve values not admitted */
   l->ConstantAttenuation = 1.0;
   l->LinearAttenuation = 0.0;
   l->QuadraticAttenuation = 0.0;
   l->Enabled = GL_FALSE;
}


/**
 * Initialize the light model data structure.
 *
 * \param lm pointer to the gl_lightmodel structure to be initialized.
 */
static void
init_lightmodel( struct gl_lightmodel *lm )
{
   ASSIGN_4V( lm->Ambient, 0.2F, 0.2F, 0.2F, 1.0F );
   lm->LocalViewer = GL_FALSE;
   lm->TwoSide = GL_FALSE;
   lm->ColorControl = GL_SINGLE_COLOR;
}


/**
 * Initialize the material data structure.
 * 
 * \param m pointer to the gl_material structure to be initialized.
 */
static void
init_material( struct gl_material *m )
{
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_AMBIENT],  0.2F, 0.2F, 0.2F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_DIFFUSE],  0.8F, 0.8F, 0.8F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_SPECULAR], 0.0F, 0.0F, 0.0F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_EMISSION], 0.0F, 0.0F, 0.0F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_SHININESS], 0.0F, 0.0F, 0.0F, 0.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_FRONT_INDEXES], 0.0F, 1.0F, 1.0F, 0.0F );
 
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_AMBIENT],  0.2F, 0.2F, 0.2F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_DIFFUSE],  0.8F, 0.8F, 0.8F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_SPECULAR], 0.0F, 0.0F, 0.0F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_EMISSION], 0.0F, 0.0F, 0.0F, 1.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_SHININESS], 0.0F, 0.0F, 0.0F, 0.0F );
   ASSIGN_4V( m->Attrib[MAT_ATTRIB_BACK_INDEXES], 0.0F, 1.0F, 1.0F, 0.0F );
}


/**
 * Initialize all lighting state for the given context.
 */
void
_mesa_init_lighting( GLcontext *ctx )
{
   GLuint i;

   /* Lighting group */
   for (i = 0; i < MAX_LIGHTS; i++) {
      init_light( &ctx->Light.Light[i], i );
   }
   make_empty_list( &ctx->Light.EnabledList );

   init_lightmodel( &ctx->Light.Model );
   init_material( &ctx->Light.Material );
   ctx->Light.ShadeModel = GL_SMOOTH;
   ctx->Light.Enabled = GL_FALSE;
   ctx->Light.ColorMaterialFace = GL_FRONT_AND_BACK;
   ctx->Light.ColorMaterialMode = GL_AMBIENT_AND_DIFFUSE;
   ctx->Light.ColorMaterialBitmask = _mesa_material_bitmask( ctx,
                                               GL_FRONT_AND_BACK,
                                               GL_AMBIENT_AND_DIFFUSE, ~0,
                                               NULL );

   ctx->Light.ColorMaterialEnabled = GL_FALSE;
   ctx->Light.ClampVertexColor = GL_TRUE;

   /* Lighting miscellaneous */
   ctx->_ShineTabList = MALLOC_STRUCT( gl_shine_tab );
   make_empty_list( ctx->_ShineTabList );
   /* Allocate 10 (arbitrary) shininess lookup tables */
   for (i = 0 ; i < 10 ; i++) {
      struct gl_shine_tab *s = MALLOC_STRUCT( gl_shine_tab );
      s->shininess = -1;
      s->refcount = 0;
      insert_at_tail( ctx->_ShineTabList, s );
   }

   /* Miscellaneous */
   ctx->Light._NeedEyeCoords = GL_FALSE;
   ctx->_NeedEyeCoords = GL_FALSE;
   ctx->_ModelViewInvScale = 1.0;
}


/**
 * Deallocate malloc'd lighting state attached to given context.
 */
void
_mesa_free_lighting_data( GLcontext *ctx )
{
   struct gl_shine_tab *s, *tmps;

   /* Free lighting shininess exponentiation table */
   foreach_s( s, tmps, ctx->_ShineTabList ) {
      _mesa_free( s );
   }
   _mesa_free( ctx->_ShineTabList );
}