Firstly, does said analogue exist?
Secondly, how to find its 4d-volume/hyper-volume given 4 vectors for sides, ideally using dot, cross product, etc.
Thirdly, what would be the 3D analogue to surface area? Eg. 1D-Arc length, 2D-Surface area, 3D- Volume, 4D-?
What you are describing is generalized using the determinant.
nD object embedded in an nD space
For objects using all dimensions, e.g., a parallelogram in 2D or a parallelepiped in 3D, put the n
vectors defining the sides of the (hyper-)parallelepiped as rows of a matrix and compute the determinant:
2D 3D 4D 5D
|x1 y1| |x1 y1 z1| |x1 y1 z1 w1| (Repeat the same pattern)
|x1 y2| |x2 y2 z2| |x2 y2 z2 w2|
|x3 y3 z3| |x3 y3 z3 w3|
|x4 y4 z4 w4|
Note that the obtained (hyper-)volume is signed, depending on the orientation of the vectors. It is thus possible to have negative volumes.
(n-1)D object embedded in nD space
For objects using one dimension less than the space in which they live, e.g., a parallelogram in 3D space, you can use the cross-product (which derives from the determinant) or a generalization of the cross-product. For example, The area of a parallelogram embedded in 3D defined by two 3D vector (x1,y1,z1)
and (x2,y2,z2)
is calculated from matrix containing the two vectors as rows:
[x1 y1 z1]
[x2 y2 z2]
From this matrix, simply create all combinations of 2x2 sub-matrix, calculate the determinant of each matrix, and put them in a vector as such
[|y1 z1|, |z1 x1|, |x1 y1|] = (y1*z2-z1*y1, z1*x2-x1*z2, x1*y2-y1*x2)
[|y2 z2| |z2 x2| |x2 y2|]
You obtain a vector, and the length of this vector is the area of the parallelogram: sqrt((y1*z2-z1*y1)^2 + (z1*x2-x1*z2)^2 + (x1*y2-y1*x2)^2)
.
The (Almost-)Ultimate Generalization
From this last example, we can create a general recipe that works for any object embedded in any dimension (yes, you can calculate the volume of a 3D parallelepiped embedded in a 17D space):
Note that this last recipe gives the unsigned volume since you square then take the square-root.
Final note: Obviously, this answer is more of a recipe than an explanation of why all these calculations work. For more information on this subject, I suggest you to look into Exterior Algebra, which is a formalism that uses the wedge product (a generalization of the cross-product) to define these hyper-volumes in a very general way.