+/**********************************************************************/
+/***** Lighting computation *****/
+/**********************************************************************/
+
+
+/*
+ * Notes:
+ * When two-sided lighting is enabled we compute the color (or index)
+ * for both the front and back side of the primitive. Then, when the
+ * orientation of the facet is later learned, we can determine which
+ * color (or index) to use for rendering.
+ *
+ * KW: We now know orientation in advance and only shade for
+ * the side or sides which are actually required.
+ *
+ * Variables:
+ * n = normal vector
+ * V = vertex position
+ * P = light source position
+ * Pe = (0,0,0,1)
+ *
+ * Precomputed:
+ * IF P[3]==0 THEN
+ * // light at infinity
+ * IF local_viewer THEN
+ * _VP_inf_norm = unit vector from V to P // Precompute
+ * ELSE
+ * // eye at infinity
+ * _h_inf_norm = Normalize( VP + <0,0,1> ) // Precompute
+ * ENDIF
+ * ENDIF
+ *
+ * Functions:
+ * Normalize( v ) = normalized vector v
+ * Magnitude( v ) = length of vector v
+ */
+
+
+
+static void
+validate_shine_table( struct gl_context *ctx, GLuint side, GLfloat shininess )
+{
+ TNLcontext *tnl = TNL_CONTEXT(ctx);
+ struct tnl_shine_tab *list = tnl->_ShineTabList;
+ struct tnl_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] = 0.0F;
+ if (shininess == 0.0F) {
+ for (j = 1 ; j <= SHINE_TABLE_SIZE ; j++)
+ m[j] = 1.0F;
+ }
+ else {
+ for (j = 1 ; j < SHINE_TABLE_SIZE ; j++) {
+ GLfloat t, x = j / (GLfloat) (SHINE_TABLE_SIZE - 1);
+ if (x < 0.005F) /* underflow check */
+ x = 0.005F;
+ t = powf(x, shininess);
+ if (t > 1e-20F)
+ m[j] = t;
+ else
+ m[j] = 0.0F;
+ }
+ m[SHINE_TABLE_SIZE] = 1.0F;
+ }
+
+ s->shininess = shininess;
+ }
+
+ if (tnl->_ShineTable[side])
+ tnl->_ShineTable[side]->refcount--;
+
+ tnl->_ShineTable[side] = s;
+ move_to_tail( list, s );
+ s->refcount++;
+}
+
+
+void
+_tnl_validate_shine_tables( struct gl_context *ctx )
+{
+ TNLcontext *tnl = TNL_CONTEXT(ctx);
+ GLfloat shininess;
+
+ shininess = ctx->Light.Material.Attrib[MAT_ATTRIB_FRONT_SHININESS][0];
+ if (!tnl->_ShineTable[0] || tnl->_ShineTable[0]->shininess != shininess)
+ validate_shine_table( ctx, 0, shininess );
+
+ shininess = ctx->Light.Material.Attrib[MAT_ATTRIB_BACK_SHININESS][0];
+ if (!tnl->_ShineTable[1] || tnl->_ShineTable[1]->shininess != shininess)
+ validate_shine_table( ctx, 1, shininess );
+}
+
+