This study addresses key challenges in obtaining reliable infrared data for maritime ship observation and limitations of existing models, such as simplified reflectance assumptions and incomplete multi-band coverage. To improve modeling accuracy and computational efficiency, a high-precision Bidirectional Reflectance and Pseudo-random Vector Enhanced Reverse Monte Carlo Method (BP-ERMCM) is developed. By combining the Bidirectional Reflectance Distribution Function (BRDF), pseudo-random vector approaches, and improved ray-tracking algorithms with precomputed thermal radiation and MODTRAN’s atmospheric transfer model, BP-ERMCM provides multi-view infrared characteristic simulations across 3–5 μm and 8–12 μm bands. Simulations using a 3D ship model with 191 viewpoints reveal seasonal sensitivity, with summer peak intensity at 9.8 μm being 39.3% higher than in winter, and viewpoint dependency showing oblique overhead radiation 5.65 times greater than that from bow angles. Long-wave contours enhance target distinction, while mid-wave regions are dominated by reflection, increasing intensity at 3.8 μm by 56.1–85.7%. These findings highlight BP-ERMCM’s potential to inform infrared signature database construction, detector optimization, and maritime observation strategies. The findings underscore BP-ERMCM’s capability to enhance efficiency and accuracy, providing valuable insights for infrared databases, sensor selection, and maritime observation strategies, thereby advancing infrared signature analysis in maritime applications.

To address the high computational complexity of evaluating the infrared radiation characteristics of combined multi-regular triangular pyramid cavity structures and the low efficiency of direct numerical simulation, this paper proposes an equivalent modeling and computational method for infrared characteristics based on cavity radiation theory. Taking a regular icosahedral corner reflector as the object of study, the complex multi-cavity structure is first decomposed into several regular triangular pyramid cavity units. Based on cavity radiation theory, first- and second-order approximate models for the effective emissivity of the opening of a single regular triangular pyramid cavity are derived, and the average effective emissivity is then determined in conjunction with geometric relationships. Subsequently, using the calculated effective emissivity of a single cavity, the multi-cavity composite structure is radiatively equivalent to a regular solid with the same outer contour and uniform surface emissivity, thereby enabling rapid calculation of the infrared radiation characteristics of the complex target. An observation network comprising 82 viewpoints was constructed, and simulation-based validation was conducted under varying temperature, size, and material-emissivity conditions. Based on the data analysis, an empirical correction term was subsequently introduced to compensate for the errors. The results show that, within the emissivity range of 0.2–0.9, the average error between the corrected equivalent model and the simulation results of the original complex structure can be controlled within 1%. Moreover, the model exhibits good stability with respect to variations in target temperature and geometric size. While maintaining computational accuracy, the proposed method improves computational efficiency by approximately 3.8 times compared with direct simulation. The study demonstrates that the proposed method can effectively preserve the main infrared radiation characteristics of combined multi-regular triangular pyramid cavity structures and can provide methodological support for the rapid evaluation and engineering design of the infrared characteristics of such complex cavity targets.