In this paper, a new approach is presented to find the 3D shape-generating profiles of different types of cutters for constructing the G-buffer models for 5-axis machining. The G-buffer for 3-axis machining is natural because the tool has only three degrees of freedom (x,y,z) for the configuration space. Five-axis machining has five degrees of freedom, and two of them are non-Euclidean. The traditional G-buffer method cannot be directly used for 5-axis machining due to the complex tool motions. In this paper, the analytic 3D shape-generating profiles are formulated to construct the swept envelope in 5-axis tool motion. The enhanced G-buffer models are updated by the constructed 5-axis swept envelope. A generalized cutter geometry, which represents different types of endmills, is used in this study. The techniques presented in this paper can be used for 5-axis tool path generation and the machined surface error analysis. Computer implementation and illustrative examples are presented in this paper.