vector plot in 3d
vec3d(g,x,y,z)
vector of rectangular coordinates of points to be plotted
vector of dimension (length(x),length(y),length(z),3) which gives magnitude and direction of vector field at each point of 3d space formed by x,y and z.
vec3d(g,x,y,z) generates a vector plot of points in x,y,z and magniude and direction given by g. Used explicitly in functions emtcurl and emtgrad.