This interactive 3D terrain generator visualizes a heightmap as a textured, three-dimensional surface. The example uses Three.js with WebGL rendering to build a `PlaneGeometry` mesh, displacing vertices based on pixel data from a CSV or PNG image via `getImageData`. A custom fragment shader blends multiple textures—ocean, sand, grass, rock, and snow—across elevation bands, using `smoothstep` for gradual transitions. D3’s `csv` function loads the height data, while `OrbitControls` enables user rotation and zoom. The scene includes a checkerboard ground plane and displays the terrain with lighting from a Phong reflection model.