Assuming you have two sets of vertex lists, pointsA & pointsB, and two sets of face lists, facesA and facesB, you probably want to stack both sets and update the lower face list. The solution is shown in the demo program below:
% create paired surfaces
gridx = repmat(linspace(-1,1,5),5,1);
gridy = repmat(transpose(linspace(-1,1,5)),1,5);
pointsA = [reshape(gridx,5^2,1) reshape(gridy,5^2,1) zeros(5^2,1)+rand(25,1)/10];
pointsB = [reshape(gridx,5^2,1) reshape(gridy,5^2,1) ones(5^2,1)+rand(25,1)/10];
% triangulate
facesA = delaunay(pointsA(:,1), pointsA(:,2));
facesB = delaunay(pointsB(:,1), pointsB(:,2));
% % visualize
trisurf(facesA, pointsA(:,1), pointsA(:,2), pointsA(:,3));
colormap jet % Default color map.
set(gca, 'Position', [0 0 1 1]); % Fill the figure window.
axis equal vis3d; % Set aspect ratio.
shading interp; % Interpolate color across faces.
camlight left; % Add a light over to the left somewhere.
lighting gouraud; % Use decent lighting.
hold on;
% visualize
trisurf(facesB, pointsB(:,1), pointsB(:,2), pointsB(:,3));
colormap jet % Default color map.
set(gca, 'Position', [0 0 1 1]); % Fill the figure window.
axis equal vis3d; % Set aspect ratio.
shading interp; % Interpolate color across faces.
camlight left; % Add a light over to the left somewhere.
lighting gouraud; % Use decent lighting.
pause(2);
% stack the vertex lists
points = vertcat(pointsA, pointsB);
% update the face list
faceUpdate = facesB+max(max(facesA));
faces = vertcat(facesA,faceUpdate);
close(gcf);
% visualize merged surfaces
trisurf(faces, points(:,1), points(:,2), points(:,3));
colormap jet % Default color map.
set(gca, 'Position', [0 0 1 1]); % Fill the figure window.
axis equal vis3d; % Set aspect ratio.
shading interp; % Interpolate color across faces.
camlight left; % Add a light over to the left somewhere.
lighting gouraud; % Use decent lighting.
Hope this helps
Thomas
