My first hypothesis was to project a texture onto a model and find a way to prevent it from following the camera, or to hook the uv coordinates up to the movement of the model, or to work some crazy math in a shader, but I decided that sometimes the simpler answer can be more effective. Having dealt with scaling UVs connected to model scale on the vine in my last film, I know a lot of heartache can be saved by cutting losses in the 3D environment and working in a compositing program.
So I plotted out the steps I would need to take to get the proper alphas I would need to create an edge shader in which the middle of the model was transparent.
To summarize my steps quickly:
1. Create an edge shader with an alpha as the inner model
2. Render separate black and white images as alphas for the whole model
3. Compositing in after effects using alpha mattes
1. Creating the Edge Shader
2. So Many Alphas!
3. Compositing is Magic
Next, I used the "full alpha" as an alpha inverted track matte...
and dropped the edge images on top! Starting to look pretty slick!