Two coherent point sources sit on a flat surface and each radiate an identical periodic disturbance outward as expanding circles. At every point on the surface, the two waves add together — the principle of superposition — and the combined height is rendered as a 3D mesh, colour-coded from deep blue (a trough) to bright cyan (a crest).
Ripple tanks used in classic physics classrooms show exactly this pattern with real water and two dipping paddles. The bright/dark radial "spokes" you see in a ripple tank photo are the antinode and node lines this simulation reproduces mathematically, extended here to non-sinusoidal wave shapes a ripple tank can't easily produce.
A 3D water-surface mesh from two coherent point sources shows how swapping a pure sine wave for a square, triangle or sawtooth wave reshapes the interference pattern, because non-sinusoidal waves are sums of many harmonics that each interfere at their own wavelength.
Two point sources radiate an identical periodic waveform outward as expanding circles. Superposition sums the two waves at every point on the surface; the mesh height and colour show the resulting constructive (crest) and destructive (trough) regions.
Pick a waveform, then adjust frequency, source separation, phase difference and amplitude. Watch the fringe pattern change shape — sine gives smooth, evenly spaced fringes; square and sawtooth give sharper, less regular ones.
A square wave is mathematically a sine fundamental plus an infinite series of odd harmonics (3f, 5f, 7f...). Each harmonic interferes at its own wavelength, which is why non-sinusoidal interference patterns look noticeably different from the sine case even with identical sources.