Libfbm is a C++ library for fast and accurate bulk-simulation of multi-dimensional (1D, 2D, 3D, .., 8D) Gaussian stationary processes, fractional Brownian motion, and fields with power-law power spectrum. It makes use of the circulant matrix embedding and FFT. Random number generation is provided by SFMT (SIMD-optimized Mersenne Twister) with a ziggurat based algorithm for normal distribution. For FFT functions, it depends on the FFTW library.
HEALPix is a set of scientific tools implementing the Hierarchical Equal Area isoLatitude Pixelation of the sphere. As suggested in the name, this pixelation produces a subdivision of a spherical surface in which every single pixel covers the same surface area. HEALPix provides various programs and libraries in C, C++, Fortran, GDL/IDL, Java, and Python which facilitate discretization, simulation, processing, analysis, and visualization of data on the sphere up to very high resolution. It is the state-of-the-art program used in astronomy and cosmology to deal with massive full-sky data sets.