VMD version 1.9.1 adds many new visualization and analysis features, and includes updated GLSL shaders for fast point sprite style sphere rendering. VMD uses GPUs to accelerate many of the most computationally demanding visualization and analysis features of interest to biomedical researchers. VMD 1.9.1 advances these capabilities further, adding a CUDA-accelerated implementation of the new QuickSurf molecular surface representation, enabling smooth trajectory animation for moderate sized biomolecular complexes consisting of a few hundred thousand to one million atoms, and interactive display of molecular surfaces for multi-million atom complexes, e.g. large virus capsids. VMD 1.9.1 also includes a new CUDA/OpenGL interop fast path to reduce host-device copies for triangle meshes produced by data-parallel CUDA kernels, and improves support for OpenCL across the board.