A system includes a computer programmed to detect a first and a second object in received image data, determine a mesh of cells on each of the first and second object surface, upon identifying a cell of the mesh on the first object mismatched to a corresponding cell on the second object to refine the mismatched cell to a plurality of cells, wherein identifying the mismatch is based on a at least one of a mismatch in a color, texture, shape, and dimensions, stop refining the cell upon determining that a refinement of the refined cell of the first object results in a refined cell that is matched to a corresponding refined cell of the second object, and output location data of mismatched cells of the first and second objects. A mismatched cell has at least one of a color mismatch, texture mismatch, and shape mismatch.