你写的是等价于这样做的指针运算：

  T x [D] [H] W]。 

 x [i] [j] [k]; //指针运算在这里
 

显然，根据你如何订购 D ， H 和 W （或 i ， j ， k ），计算将不同。

in C++, what is the indexing value for a W * H * D sized 3D array?

for a particular i, j, k is this the correct indexing:

i*W*H+j*W+k

What you have written is equivalent to the pointer arithmetic that this would do:

T x[D][H][W];

x[i][j][k];  // Pointer arithmetic done here

Obviously, depending on how you order D, H and W (or i, j, k), the calculation will differ.