Simulating Tectonic Plates for Game Worlds

Procedural world generators simulate tectonic plate collisions by modeling crustal kinematics, edge interactions, and geological uplift instead of relying entirely on standard heightmap noise. By defining distinct plate boundaries, assigning directional velocities, and applying physics-inspired deformation rules where plates meet, developers can produce realistic mountain chains, volcanic arcs, and ocean trenches that make virtual worlds feel authentic.

To begin the simulation, the generator divides the terrain map or planetary sphere into discrete plates. This is commonly achieved using a Voronoi diagram or Delaunay triangulation seeded with a randomized set of points. Each resulting cell or polygon cluster represents an individual tectonic plate. Developers assign properties to each plate, most notably crust type (dense, thin oceanic crust versus buoyant, thick continental crust) and an initial motion vector representing speed and direction of travel.

Once motion is assigned, the system evaluates the boundaries where adjacent plates interact. By calculating the dot product of the relative velocity vectors between neighboring plates along their shared borders, the generator classifies the boundary into one of three primary geological types: divergent (pulling apart), transform (sliding past each other), or convergent (colliding). Convergent boundaries are the focus for mountain formation.

When a convergent boundary is detected, the algorithm determines the nature of the collision based on crust density:

• Continental-Continental Convergence: Because both crusts are buoyant, neither easily subducts into the mantle. The generator simulates massive crustal crumpling and folding. The heightmap values along the boundary are increased significantly over a wide zone, generating massive, rugged mountain ranges like the Himalayas.
• Oceanic-Continental Convergence: The denser oceanic plate is forced downward beneath the lighter continental plate in a subduction zone. The generator lowers the ocean side to create deep marine trenches, while the continental edge undergoes uplift combined with volcanic activity, producing linear mountain ranges like the Andes.
• Oceanic-Oceanic Convergence: One oceanic plate subducts under the other, which the generator typically models by placing curving chains of volcanic islands (island arcs) alongside deep trenches.

To translate these boundary collisions into actual terrain heightmaps, generators apply structural deformation techniques. Instead of directly applying uniform height, developers often project perpendicular force vectors along the fault lines. Algorithms distribute uplift using mathematical profiles—such as Gaussian distributions or custom curve falloffs—perpendicular to the collision axis. Perlin, Simplex, or Worley noise is layered along the collision axis to introduce localized irregularities, jagged ridgelines, and jagged peaks, avoiding an artificial, uniform look.

Finally, the raw tectonic heightmap serves as a macro-level foundation for erosion passes. Developers run hydraulic and thermal erosion algorithms over the uplifted regions. Water simulation carves river networks, talus slopes, and valleys into the rising landmasses, distributing sediment downward. This combination of macro-scale plate kinematics and micro-scale erosion produces geologically consistent mountain ranges that mirror real-world terrain dynamics.