[Fieldtrip] getting FieldTrip to build again

[Daniel Bergey]

I'm working on getting FieldTrip to build.  What approach would be most
likely to be merged upstream?  I'll concentrate there.

Option 1: build against old OpenGL
I have ugly patches to do this, mostly by specifying upper version
limits in the cabal file.  Ugly in that I introduce at least one
exported function with GLfloat in the type, and I'm not sure how hard it
will be to make that go away.

Option 2: build against new HOpenGL
This means accepting that all the rendering code needs GLfloat or
GLdouble.  It seems reasonable to keep all that in one module, and only
export polymorphic functions which accept normal haskell types.  There
are many more design decisions to be made than for Option 1.

For instance, where does the abstraction barrier belong?  My current
thinking is that tesselation shouldn't depend on OpenGL, so I'll need a
data structure to hold triangles.  STL export would use the tesselation
code, but not the rendering code.  Downsides include not taking
advantage of OpenGL's compact formats for triangles, or else
contaminating the triangle representation with knowledge of how OpenGL
does things.

I haven't thought yet about the equivalent abstraction for color
information.

Thanks,
Daniel