1. A computer-implemented process for constructing virtual environments, comprising: using a computer to perform process actions for: generating environmental information by scanning a real-world environment to classify geometry of surfaces and objects within that environment; receiving a master set of virtual building blocks, each virtual building block including a plurality of characteristics and including semantic and geometric constraints relating to the virtual building blocks; procedurally molding a physically constrained virtual environment by iteratively optimizing a layout of an automatically selected variable subset of the virtual building blocks relative to a scene-specific cost function; each iteration of optimized layout of the physically constrained virtual environment being consistent with the characteristics and constraints of the subset of virtual building blocks, and the environmental information of the real-world environment; the scene-specific cost function being derived for each iteration from the characteristics and constraints of the subset of virtual building blocks in combination with the environmental information; displaying the physically constrained virtual environment via a display device, such that at least a portion of the physically constrained virtual environment is anchored to the real-world environment in a way that at least partially matches tactile truth for one or more surfaces and objects within the real-world environment.