spline fitting multiple variables

Hello, I am fairly new to curve fitting trying to figure out how a pp form spline fit was done and how to plot it in various ways. Here is the details of the function.

form: 'pp'

breaks: {[1x5 double] [1x27 double] [0 1 2 3 4]}

coefs: [4-D double]

pieces: [4 26 4]

order: [4 4 4]

dim: 1

The data was collected in a test and I believe I am working with a function such as: z=f(a,b,c)

The test goes like this: z is recorded for a range of a (-10 to 10) for 5 different values of b (0 to 4) and 5 different values of c (0 to 4), for a total of 25 test "runs".

runs would look like this:

run1

z=recoded value

a=sweep from -10 to 10

b=0

c=0

run2

z=recoded value

a=sweep from -10 to 10

b=1

c=0

run3

z=recoded value

a=sweep from -10 to 10

b=2

c=0

etc.

If someone can give tips on how fits are done with data such as this and ways to plot it would be much appreciated.