Waves of Grain from Keith Skretch on Vimeo
The series of images 29-36 seconds through Waves of Grain
So what can you do with this data? Well you can reproject to give you a virtual view of what the left and the front sides of the blocks of wood would have looked like:
Again, quite cool. But you can still do more. Because this is now a purely digital representation of this block of wood you can display it in ways that would be physically impossible to make. Instead of just looking at the outside of the block...
... you can now look inside.
This 3D reconstruction lets you see how the growth rings appear in three dimensions, showing exactly where the grain runs. It lets you see how the knot, which is where a branch grew from the tree, cuts through the growth rings in a distinctive way. It lets you see pretty much everything about the internal structure of the wood!
This kind of approach is used all over biology, and is normally called something like serial sectioning. You can use it for everything from reconstructing a whole person by histology and a light microscope to a single cell by electron microscopy.
ImageJ: 3D reconstructions