load_GDF ValueError about meshmagick

[michaelcdevin]

I discovered the problem I was having. If I'm understanding the code correctly, load_GDF assumes that each point is contained on its own line, so each face consists of four lines before moving on to the next face. For example:

X1(1)   Y1(1)   Z1(1)
X2(1)   Y2(1)   Z2(1)
X3(1)   Y3(1)   Z3(1)
X4(1)   Y4(1)   Z4(1)
X2(1)   Y2(1)   Z2(1)
X2(2)   Y2(2)   Z3(2)
...
X4(nf)  Y4(nf)  Z4(nf)

My GDF file contains all four points of each face on one line:

X1(1)   Y1(1)   Z1(1)   X2(1)   Y2(1)   Z2(1)   X3(1)   Y3(1)   Z3(1)   X4(1)   Y4(1)   Z4(1)
X1(2)   Y1(2)   Z1(2)   X2(2)   Y2(2)   Z2(2)   X3(2)   Y3(2)   Z3(2)   X4(2)   Y4(2)   Z4(2)
...
X1(nf)  Y1(nf)  Z1(nf)  X2(nf)  Y2(nf)  Z2(nf)  X3(nf)  Y3(nf)  Z3(nf)  X4(nf)  Y4(nf)  Z4(nf)

According to the WAMIT documentation, line breaks must exist between faces, but additional line breaks can also be used without effect, so either format above is acceptable. However, load_GDF starts returning empty arrays once it reaches the end of the file with the second format because it is trying to read four times as many lines as the GDF file contains, resulting in the ValueError I encountered.

I modified my local version of meshmagick.mmio.load_GDF to generalize how it reads the points in the file so either format is acceptable (or really any format as long as there is a line break at the end of each face). I will create a pull request with my changes.