In multi-axis machining of dies and molds with complex sculptured surfaces, numerical control (NC) simulation/verification is a must for the avoidance of expensive rework and material waste. Despite the fact that NC simulation has been extensively used by industries for many years, efficient, accurate, and reliable view-independent simulation of multi-axis NC machining still remains a difficult challenge. This paper presents the use of adaptive voxel data structure in conjunction with the modeling of a universal cutter for the development of an efficient and reliable multi-axis (typically five-axis) simulation procedure. The octree-based voxel representation of the workpiece saves a significant amount of memory space without sacrificing the simulation accuracy. Rendering of the voxel-based model is view independent and does not suffer from any aliasing effect, due to the real-time triangulation of the boundary surfaces using an extended marching cube algorithm. Implicit algebraic equations are used to model the automatically programed tool geometry, which can represent a universal cutter with high precision. In addition, the proposed method allows users to perform error analysis and gouging detection by comparing the machined surfaces with the original computer-aided design (CAD) model. Illustration of the implementation and experimental results demonstrate that the proposed method is reliable, accurate, and highly efficient.