Posted by: Roger King
3D animation, 3D modeling, Maya
One of the things I teach is 3D animation (using Autodesk Maya). I also happen to have had cornea transplant surgery in both of my eyes, as a result of a degenerative disease that caused my corneas to thin gradually, thereby losing their structural integrity. The corneas, by the way, are the clear outer surface of the eye.
This is the second blog posting in a series relating to the use of modeling and animation software to develop technology to assist folks with limited vision caused by deformed corneas.
The problem with my corneas was that they were not smoothly curved. Why? Because my corneas had grown thin, their slope varied somewhat erratically. In other words, my corneas were not smooth like a basketball. There were bumps and folds throughout their surfaces. Thus, light passing through them wasn’t properly focused, the way it would be if it passed through perfectly spherical corneas.
Since my corneas didn’t do their job of pre-focusing light, my lenses could not do their jobs by completing the focusing of light. So, the world was choppy and filled with multiple, overlapping images. It was like looking through a kaleidoscope. The disease is called keratoconus.
An idea from the world of 3D animation.
In my research at the University of Colorado, I have been looking into the following approach. The overall idea is to create an inverted, deformed view that compensates for the distortion caused by a person’s irregularly shaped cornea.
The first step is to use Maya to create translucent hemisphere with varying slopes, thus simulating the effects of keratoconus. The hemisphere would be created by inputting a map of the varying slope of the user’s cornea. These maps can be quickly and cheaply made by using equipment commonly found in the offices of opthomologists.
The second step involves automatically creating a compensating view, by making use of deformer primitives in Maya. The way in which the deformer primitives are used to create the compensating view would be calculated from the topographical map of the diseased cornea. The view would at least partially undo the deformations caused by the diseased cornea.
In the third step, the individual with a deformed cornea could look through this software-generated view while looking at written text, webpages, images, and the like. This would be done by moving the material to be viewed into a Maya scene, and then rendering it from the perspective of someone looking through this compensating view. The user would look at this distorted version of the visual material, which for the user with the bad cornea, would look better than the original.
Rather than trying to compute the shape of a compensating, deformed view and then building this with Maya, a different approach involves allowing a user with deformed corneas to interactively deform their view by using Maya deformers.
First, whatever material is being viewed would be read into the animator’s design window in Maya.
Second, the user could manipulate the view until the material being viewed becomes viewable. This distorted view would then be used to create a deformation template that could be applied to any material that the user needs to view.
Again, in the third step, the material would be read into a Maya scene, deformed, and then rendered for the user to view.
And another approach.
There is a serious problem that complicates these two approaches, and that is that a weak cornea is, by its very nature, unstable, and so the deformities caused by it shift constantly.
So, another way to attack the problem involves simulating the effect of placing a large “scleral” lens that straddles most of the eye. We will look at this idea in the next posting of this blog…