Open-celled foam is modeled as a network of struts formed by the nucleation, growth and intersection of uniform spherical bubbles arranged in a regular three-dimensional array. The number of struts per unit cell and their characteristic geometry and orientations depend on the bubble-centering algorithm chosen to define the array and on the degree of bubble intersection. A foam model based on a body-centered cubic arrangement of uniform spherical bubbles is used to compare strut geometries over a range of bubble interferences. The model predictions are compared to the microstructures observed in amorphous carbon foam. The significance of these idealized foam results for graphitic carbon foams is discussed.