A 3D simulation of diffraction from crystal structures and Bravais lattices that generates diffraction patterns in a lab setup. Crystal lattice parameters, crystal orientation, incident wavelength and other parameters are adjustable in real time to produce a diffraction pattern on an adjustable screen as in a laboratory experiment. Menu choices select from the five 2D and fourteen 3D bravais lattices and from the common crystal structures of diamond, sodium chloride, cesium chloride, zincblende or hexagonal close packed. A 3D plot of the diffraction pattern intensity is presented together with an adjustable 2D section from th 3D plot that allows analysis of the size and separation of diffraction maxima and minima.