A method comprising: capturing first 3D model data (207; 309) relating to each of a first plurality of voxels (212v 214v; 305v), the first 3D model data relating to an object and for forming a first 3D model of the object including capturing a first plurality of images (209a, 209c; 301f, 302f, 303f, 304f) of the object wherein each of the first plurality of images comprises at least one pixel and has overlapping fields of view of the object, said first plurality of images being stored as first image data; correlating the first image data of the object with the first 3D model data to produce a first index, the first index indicating a correlation between at least one pixel (211a, 211c, 213a, 213c; 301p 302p, 303p, 304p) of an image of the first plurality of images and at least one voxel (212v, 214v; 305v) of the first 3D model data, each of said at least one pixel and said at least one voxel representing a same portion of said object; and storing the first index for retrieval, wherein the method further comprises: flagging a first voxel of the first plurality of voxels for monitoring over time capturing second 3D model data relating to each of a second plurality of voxels, the second 3D model data relating to the object and for forming a second 3D model of the object including capturing a second plurality of images of the object wherein each of the second plurality of images comprises at least one pixel and has overlapping fields of view of the object, said second plurality of images being stored as second image data; correlating the second image data of the object with the second 3D model data to produce a second index, the second index indicating a correlation between at least one pixel of an image of the second plurality of images and at least one voxel of the second 3D model data; storing the second index for retrieval; and correlating the second 3D model with the first 3D model to correlate the second index and the first index. capturing first 3D model data (207; 309) relating to each of a first plurality of voxels (212v 214v; 305v), the first 3D model data relating to an object and for forming a first 3D model of the object including capturing a first plurality of images (209a, 209c; 301f, 302f, 303f, 304f) of the object wherein each of the first plurality of images comprises at least one pixel and has overlapping fields of view of the object, said first plurality of images being stored as first image data; correlating the first image data of the object with the first 3D model data to produce a first index, the first index indicating a correlation between at least one pixel (211a, 211c, 213a, 213c; 301p 302p, 303p, 304p) of an image of the first plurality of images and at least one voxel (212v, 214v; 305v) of the first 3D model data, each of said at least one pixel and said at least one voxel representing a same portion of said object; and storing the first index for retrieval, flagging a first voxel of the first plurality of voxels for monitoring over time capturing second 3D model data relating to each of a second plurality of voxels, the second 3D model data relating to the object and for forming a second 3D model of the object including capturing a second plurality of images of the object wherein each of the second plurality of images comprises at least one pixel and has overlapping fields of view of the object, said second plurality of images being stored as second image data; correlating the second image data of the object with the second 3D model data to produce a second index, the second index indicating a correlation between at least one pixel of an image of the second plurality of images and at least one voxel of the second 3D model data; storing the second index for retrieval; and correlating the second 3D model with the first 3D model to correlate the second index and the first index. <EOS>