Slide 28 of 42
Okay, now the second part of the opacity function generation, the
boundary emphasis function. This is controlled by the user, and it
allows the user to dictate the character of the rendered boundary.
So, for example, the user can say something like, "I want my rendered
bounaries to be two voxels thick, with soft edges, and offset half a
voxel, towards the interior of the object". And, here's the boundary
emphasis function which captures that intent- two voxels wide, ramped
edges, and shifted half a voxel upward, towards higher positions, towards
the inside of the object. I would suggest that
this position domain is a more intuitive domain to work in, and is a
smaller parameter space, because the user is really just controlling the
size, shape, and location of this single peak in the boundary emphasis
function. And then again, to reiterate, the semi-automatically generated
opacity function is alpha(v) equals b(p(v)).
