PART 2: MODELING THE SURFACE
OF THE CORTEX
Making the folds. Using Adobe Illustrator I traced the wrinkles
in each of the 6 views of the brain.
The thick yellow lines represent the wrinkles and the thin
black lines represent a general midpoint between wrinkles. After drawing
these lines I turned them into outline shapes so I could drill them onto
the sides of the brain model. The small red and blue squares are the points
that will make up the final brain mesh.
I saved the red dots, blue dots and lines as separate ceps files. I end
up with 3 ceps files for each of the six
view, giving me a total of 18 CEPS files to import into Modeler :(
I imported the line CEPS files into Modeler and extruded them
so they intersected the brain shape.
I then used the Solid Drill command (on Modeler's Multiply
tab) to Stencil a new surface on the brain shape.
I did the same with each of the 6 sides, and collect the resulting
parts into a layer to serve as a background guide for drawing the wrinkles.
This view shows the results of two of the 6 drill operations
repeated this process with the red and blue boxes. Once I had the boxes
drilled onto the surface, I cut them and pasted them in a new layer. I
then use the merge points command with an absolute setting large enough
to merge the little boxes into single points.
OK, now I am ready to start recreating the shape of the brain
cortex. I have the points that will make a nice quad mesh in the foreground
layer and the lines in the background layer to help me figure out how
to connect them.
Selecting four points at a time, I worked my way along the wrinkles making
quad polygons. I then did the same for the surface between the wrinkles.
Building the whole brain this way took a lot of time to finish.
The shape of the cortex recreated as a quad poly cage.
Here I have hiden the outer surface of the brain and selected
the wrinkle polygons.
I use the smooth shift command to extrude the wrinkles into
the brain. Because I had the wrinkles selected I was able to give the
polygons at the bottom of the wrinkles a different surface name.
The shape is now ready to become a smooth sub patch object.
Unfortunately this operation did not produce the ideal shaped
cage for the wrinkles. The openings of the wrinkles were too wide. So,
point by point, I worked my way along each wrinkle closing them up to
get a nice tight seem. Here about half of the wrinkles are done.
model does not look to pretty in polygon mode...
... but looks
good as a subpatch object.