If you have a surface in Visit (ie an isosurface, or a slice), you can save the window as a vtk file. And then use the attached read2DScalarVTK.m matlab function to import the vtk file as a struct in matlab. The struct returns contains

• Faces - Fx3 array of integers containing the point numbers that make up each face
• Vertices - Vx3 array of floats containing the xyz coordinates of each vertex
• FaceVertexCData - Fx1 scalar field defined on the faces