Background The traditional Monte-Carlo (MC) method faces an inherent trade-off between geometric modeling accuracy and computational efficiency when addressing real-world irregular terrain modeling.

Purpose This paper proposes a fast MC particle transport modeling method based on irregular triangular networks for complex terrains, addressing the technical challenge of achieving adaptive and efficient MC modeling under high-resolution complex terrain scenarios.

Methods The methodology consists of three key phases: First, high-resolution raster-format terrain elevation data are processed through two-dimensional wavelet transformation to precisely identify abrupt terrain variations and extract significant elevation points. Subsequently, the Delaunay triangulation algorithm is employed to construct TIN-structured terrain models from discrete point sets. Finally, the MCNP code’s “arbitrary polyhedron” macrobody definition is leveraged to establish geometric planes, with Boolean operations applied to synthesize intricate geometric entities, thereby realizing rapid automated MC modeling for high-resolution complex terrains.

Results The results demonstrate that the proposed method accurately reproduces terrain-induced effects on radiation transport, achieving high-fidelity simulations while significantly compressing the number of cells and enhancing computational efficiency.

Conclusions This methodology represents a novel approach for large-scale radiation field modeling under complex terrain constraints, demonstrating broad applicability to MC particle transport simulations in arbitrary large-scale complex terrain scenarios.