--- a/+scheme/Elastic2dVariable.m	Tue Dec 04 14:54:28 2018 -0800
+++ b/+scheme/Elastic2dVariable.m	Tue Dec 04 15:24:36 2018 -0800
@@ -31,9 +31,16 @@
         tau_l, tau_r
 
         H, Hi % Inner products
+
         phi % Borrowing constant for (d1 - e^T*D1) from R
         gamma % Borrowing constant for d1 from M
         H11 % First element of H
+
+        % Borrowing from H, M, and R
+        thH
+        thM
+        thR
+
         e_l, e_r
         d1_l, d1_r % Normal derivatives at the boundary
         E % E{i}^T picks out component i
@@ -64,6 +71,13 @@
 
             h = g.scaling();
             lim = g.lim;
+            if isempty(lim)
+                x = g.x;
+                lim = cell(length(x),1);
+                for i = 1:length(x)
+                    lim{i} = {min(x{i}), max(x{i})};
+                end
+            end
 
             % 1D operators
             ops = cell(dim,1);
@@ -77,6 +91,11 @@
                 obj.H11{i} = ops{i}.borrowing.H11;
                 obj.phi{i} = beta/obj.H11{i};
                 obj.gamma{i} = ops{i}.borrowing.M.d1;
+
+                % Better names
+                obj.thR{i} = ops{i}.borrowing.R.delta_D;
+                obj.thM{i} = ops{i}.borrowing.M.d1;
+                obj.thH{i} = ops{i}.borrowing.H11;
             end
 
             I = cell(dim,1);
@@ -262,35 +281,24 @@
         % Closure functions return the operators applied to the own domain to close the boundary
         % Penalty functions return the operators to force the solution. In the case of an interface it returns the operator applied to the other doamin.
         %       boundary            is a string specifying the boundary e.g. 'l','r' or 'e','w','n','s'.
-        %       type                is a cell array of strings specifying the type of boundary condition for each component.
+        %       bc                  is a cell array of component and bc type, e.g. {1, 'd'} for Dirichlet condition
+        %                           on the first component.
         %       data                is a function returning the data that should be applied at the boundary.
         %       neighbour_scheme    is an instance of Scheme that should be interfaced to.
         %       neighbour_boundary  is a string specifying which boundary to interface to.
-        function [closure, penalty] = boundary_condition(obj, boundary, type, parameter)
-            default_arg('type',{'free','free'});
-            default_arg('parameter', []);
+        function [closure, penalty] = boundary_condition(obj, boundary, bc, tuning)
+            default_arg('tuning', 1.2);
+
+            assert( iscell(bc), 'The BC type must be a 2x1 cell array' );
+            comp = bc{1};
+            type = bc{2};
 
             % j is the coordinate direction of the boundary
-            % nj: outward unit normal component.
-            % nj = -1 for west, south, bottom boundaries
-            % nj = 1  for east, north, top boundaries
-            [j, nj] = obj.get_boundary_number(boundary);
-            switch nj
-            case 1
-                e = obj.e_r;
-                d = obj.d1_r;
-                tau = obj.tau_r{j};
-                T = obj.T_r{j};
-            case -1
-                e = obj.e_l;
-                d = obj.d1_l;
-                tau = obj.tau_l{j};
-                T = obj.T_l{j};
-            end
+            j = obj.get_boundary_number(boundary);
+            [e, T, tau, H_gamma] = obj.get_boundary_operator({'e','T','tau','H'}, boundary);
 
             E = obj.E;
             Hi = obj.Hi;
-            H_gamma = obj.H_boundary{j};
             LAMBDA = obj.LAMBDA;
             MU = obj.MU;
             RHOi = obj.RHOi;
@@ -298,66 +306,127 @@
             dim = obj.dim;
             m_tot = obj.grid.N();
 
-            RHOi_kron = obj.RHOi_kron;
-            Hi_kron = obj.Hi_kron;
-
             % Preallocate
             closure = sparse(dim*m_tot, dim*m_tot);
-            penalty = cell(dim,1);
-            for k = 1:dim
-                penalty{k} = sparse(dim*m_tot, m_tot/obj.m(j));
-            end
+            penalty = sparse(dim*m_tot, m_tot/obj.m(j));
 
-            % Loop over components that we (potentially) have different BC on
-            for k = 1:dim
-                switch type{k}
+            k = comp;
+            switch type
+
+            % Dirichlet boundary condition
+            case {'D','d','dirichlet','Dirichlet'}
 
-                % Dirichlet boundary condition
-                case {'D','d','dirichlet','Dirichlet'}
+                phi = obj.phi{j};
+                h = obj.h(j);
+                h11 = obj.H11{j}*h;
+                gamma = obj.gamma{j};
 
-                    tuning = 1.2;
-                    phi = obj.phi{j};
-                    h = obj.h(j);
-                    h11 = obj.H11{j}*h;
-                    gamma = obj.gamma{j};
-
-                    a_lambda = dim/h11 + 1/(h11*phi);
-                    a_mu_i = 2/(gamma*h);
-                    a_mu_ij = 2/h11 + 1/(h11*phi);
+                a_lambda = dim/h11 + 1/(h11*phi);
+                a_mu_i = 2/(gamma*h);
+                a_mu_ij = 2/h11 + 1/(h11*phi);
 
-                    d = @kroneckerDelta;  % Kronecker delta
-                    db = @(i,j) 1-d(i,j); % Logical not of Kronecker delta
-                    alpha = @(i,j) tuning*( d(i,j)* a_lambda*LAMBDA ...
-                                          + d(i,j)* a_mu_i*MU ...
-                                          + db(i,j)*a_mu_ij*MU );
+                d = @kroneckerDelta;  % Kronecker delta
+                db = @(i,j) 1-d(i,j); % Logical not of Kronecker delta
+                alpha = @(i,j) tuning*( d(i,j)* a_lambda*LAMBDA ...
+                                      + d(i,j)* a_mu_i*MU ...
+                                      + db(i,j)*a_mu_ij*MU );
 
-                    % Loop over components that Dirichlet penalties end up on
-                    for i = 1:dim
-                        C = T{k,i};
-                        A = -d(i,k)*alpha(i,j);
-                        B = A + C;
-                        closure = closure + E{i}*RHOi*Hi*B'*e{j}*H_gamma*(e{j}'*E{k}' );
-                        penalty{k} = penalty{k} - E{i}*RHOi*Hi*B'*e{j}*H_gamma;
-                    end
+                % Loop over components that Dirichlet penalties end up on
+                for i = 1:dim
+                    C = T{k,i};
+                    A = -d(i,k)*alpha(i,j);
+                    B = A + C;
+                    closure = closure + E{i}*RHOi*Hi*B'*e*H_gamma*(e'*E{k}' );
+                    penalty = penalty - E{i}*RHOi*Hi*B'*e*H_gamma;
+                end
 
-                % Free boundary condition
-                case {'F','f','Free','free','traction','Traction','t','T'}
-                        closure = closure - E{k}*RHOi*Hi*e{j}*H_gamma* (e{j}'*tau{k} );
-                        penalty{k} = penalty{k} + E{k}*RHOi*Hi*e{j}*H_gamma;
+            % Free boundary condition
+            case {'F','f','Free','free','traction','Traction','t','T'}
+                    closure = closure - E{k}*RHOi*Hi*e*H_gamma* (e'*tau{k} );
+                    penalty = penalty + E{k}*RHOi*Hi*e*H_gamma;
 
-                % Unknown boundary condition
-                otherwise
-                    error('No such boundary condition: type = %s',type);
-                end
+            % Unknown boundary condition
+            otherwise
+                error('No such boundary condition: type = %s',type);
             end
         end
 
-        function [closure, penalty] = interface(obj,boundary,neighbour_scheme,neighbour_boundary,opts)
+        function [closure, penalty] = interface(obj,boundary,neighbour_scheme,neighbour_boundary)
             % u denotes the solution in the own domain
             % v denotes the solution in the neighbour domain
+            % Operators without subscripts are from the own domain.
             tuning = 1.2;
-            % tuning = 20.2;
-            error('Interface not implemented');
+
+            % j is the coordinate direction of the boundary
+            j = obj.get_boundary_number(boundary);
+            j_v = neighbour_scheme.get_boundary_number(neighbour_boundary);
+
+            % Get boundary operators
+            [e, T, tau, H_gamma] = obj.get_boundary_operator({'e','T','tau','H'}, boundary);
+            [e_v, tau_v] = neighbour_scheme.get_boundary_operator({'e','tau'}, neighbour_boundary);
+
+            % Operators and quantities that correspond to the own domain only
+            Hi = obj.Hi;
+            RHOi = obj.RHOi;
+            dim = obj.dim;
+
+            %--- Other operators ----
+            m_tot_u = obj.grid.N();
+            E = obj.E;
+            LAMBDA_u = obj.LAMBDA;
+            MU_u = obj.MU;
+            lambda_u = e'*LAMBDA_u*e;
+            mu_u = e'*MU_u*e;
+
+            m_tot_v = neighbour_scheme.grid.N();
+            E_v = neighbour_scheme.E;
+            LAMBDA_v = neighbour_scheme.LAMBDA;
+            MU_v = neighbour_scheme.MU;
+            lambda_v = e_v'*LAMBDA_v*e_v;
+            mu_v = e_v'*MU_v*e_v;
+            %-------------------------
+
+            % Borrowing constants
+            h_u = obj.h(j);
+            thR_u = obj.thR{j}*h_u;
+            thM_u = obj.thM{j}*h_u;
+            thH_u = obj.thH{j}*h_u;
+
+            h_v = neighbour_scheme.h(j_v);
+            thR_v = neighbour_scheme.thR{j_v}*h_v;
+            thH_v = neighbour_scheme.thH{j_v}*h_v;
+            thM_v = neighbour_scheme.thM{j_v}*h_v;
+
+            % alpha = penalty strength for normal component, beta for tangential
+            alpha_u = dim*lambda_u/(4*thH_u) + lambda_u/(4*thR_u) + mu_u/(2*thM_u);
+            alpha_v = dim*lambda_v/(4*thH_v) + lambda_v/(4*thR_v) + mu_v/(2*thM_v);
+            beta_u = mu_u/(2*thH_u) + mu_u/(4*thR_u);
+            beta_v = mu_v/(2*thH_v) + mu_v/(4*thR_v);
+            alpha = alpha_u + alpha_v;
+            beta = beta_u + beta_v;
+
+            d = @kroneckerDelta;  % Kronecker delta
+            db = @(i,j) 1-d(i,j); % Logical not of Kronecker delta
+            strength = @(i,j) tuning*(d(i,j)*alpha + db(i,j)*beta);
+
+            % Preallocate
+            closure = sparse(dim*m_tot_u, dim*m_tot_u);
+            penalty = sparse(dim*m_tot_u, dim*m_tot_v);
+
+            % Loop over components that penalties end up on
+            for i = 1:dim
+                closure = closure - E{i}*RHOi*Hi*e*strength(i,j)*H_gamma*e'*E{i}';
+                penalty = penalty + E{i}*RHOi*Hi*e*strength(i,j)*H_gamma*e_v'*E_v{i}';
+
+                closure = closure - 1/2*E{i}*RHOi*Hi*e*H_gamma*e'*tau{i};
+                penalty = penalty - 1/2*E{i}*RHOi*Hi*e*H_gamma*e_v'*tau_v{i};
+
+                % Loop over components that we have interface conditions on
+                for k = 1:dim
+                    closure = closure + 1/2*E{i}*RHOi*Hi*T{k,i}'*e*H_gamma*e'*E{k}';
+                    penalty = penalty - 1/2*E{i}*RHOi*Hi*T{k,i}'*e*H_gamma*e_v'*E_v{k}';
+                end
+            end
         end
 
         % Returns the coordinate number and outward normal component for the boundary specified by the string boundary.
@@ -380,8 +449,9 @@
             end
         end
 
-        % Returns the coordinate number and outward normal component for the boundary specified by the string boundary.
-        function [return_op] = get_boundary_operator(obj, op, boundary)
+        % Returns the boundary operator op for the boundary specified by the string boundary.
+        % op: may be a cell array of strings
+        function [varargout] = get_boundary_operator(obj, op, boundary)
 
             switch boundary
                 case {'w','W','west','West', 'e', 'E', 'east', 'East'}
@@ -392,29 +462,51 @@
                     error('No such boundary: boundary = %s',boundary);
             end
 
-            switch op
-                case 'e'
-                    switch boundary
-                        case {'w','W','west','West','s','S','south','South'}
-                            return_op = obj.e_l{j};
-                        case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
-                            return_op = obj.e_r{j};
-                    end
-                case 'd'
-                    switch boundary
-                        case {'w','W','west','West','s','S','south','South'}
-                            return_op = obj.d1_l{j};
-                        case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
-                            return_op = obj.d1_r{j};
-                    end
-                otherwise
-                    error(['No such operator: operatr = ' op]);
+            if ~iscell(op)
+                op = {op};
+            end
+
+            for i = 1:length(op)
+                switch op{i}
+                    case 'e'
+                        switch boundary
+                            case {'w','W','west','West','s','S','south','South'}
+                                varargout{i} = obj.e_l{j};
+                            case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
+                                varargout{i} = obj.e_r{j};
+                        end
+                    case 'd'
+                        switch boundary
+                            case {'w','W','west','West','s','S','south','South'}
+                                varargout{i} = obj.d1_l{j};
+                            case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
+                                varargout{i} = obj.d1_r{j};
+                        end
+                    case 'H'
+                        varargout{i} = obj.H_boundary{j};
+                    case 'T'
+                        switch boundary
+                            case {'w','W','west','West','s','S','south','South'}
+                                varargout{i} = obj.T_l{j};
+                            case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
+                                varargout{i} = obj.T_r{j};
+                        end
+                    case 'tau'
+                        switch boundary
+                            case {'w','W','west','West','s','S','south','South'}
+                                varargout{i} = obj.tau_l{j};
+                            case {'e', 'E', 'east', 'East','n', 'N', 'north', 'North'}
+                                varargout{i} = obj.tau_r{j};
+                        end
+                    otherwise
+                        error(['No such operator: operator = ' op{i}]);
+                end
             end
 
         end
 
         function N = size(obj)
-            N = prod(obj.m);
+            N = obj.dim*prod(obj.m);
         end
     end
 end