update docs and add default iso val of 0 for marching cubes

Author: sjkelly

src/marching_cubes.jl

@@ -278,14 +278,16 @@ const tri_table = ((-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1),
                     (-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1))
 
 """
+`marching_cubes(sdf::SignedDistanceField, [iso = 0.0,] [MT = HomogenousMesh{Point{3,Float64},Face{3,Int,0}}])`
+
 Construct a `HomogenousMesh` from a `SignedDistanceField` using the
 marching cubes algorithm. This method is faster than Marching Tetrahedra
 and generates fewer vertices and faces (about 1/4 as many).
 However it may generate non-manifold meshes, while Marching
 Tetrahedra guarentees a manifold mesh.
 """
 function marching_cubes{ST,FT,M<:AbstractMesh}(sdf::SignedDistanceField{3,ST,FT},
-                               iso,
+                               iso=0.0,
                                MT::Type{M}=HomogenousMesh{Point{3,Float64},Face{3,Int,0}})
     nx, ny, nz = size(sdf)
     h = HyperRectangle(sdf)

test/runtests.jl

@@ -38,8 +38,10 @@ sdf = SignedDistanceField(HyperRectangle(Vec(-1,-1,-1.),Vec(2,2,2.))) do v
 end
 
 m = marching_cubes(sdf,0)
+m2 = marching_cubes(sdf)
 @test length(vertices(m)) == 10968
 @test length(faces(m)) == 3656
+@test m == m2
 
 if "--profile" in ARGS
     HomogenousMesh(s2)