Thermal radiation is the dominant heat transfer mechanism in wildfires, governing both flame dynamics and fire spread through radiative preheating of unburned fuels. In physics-based wildfire models, the Finite Volume Method (FVM) is widely used to solve the 3D Radiative Transfer Equation. However, a fundamental contradiction exists between the demand for high-fidelity incident radiation predictions and the associated computational overhead. While previous research has predominantly focused on buoyancy-driven flames, this study systematically evaluates the impact of FVM angular resolution on the accuracy of surface incident radiation for both buoyancy-driven and wind-driven fire scenarios. Results show that low-resolution schemes (e.g., 16 azimuthal and 2 zenith angles) suffer from severe "ray effects"—non-physical numerical oscillations—leading to significant local heat flux errors. In calm atmosphere cases, a high resolution of at least 64–12 angles is required to eliminate artifacts and resolve the incident radiation correctly. In wind-driven scenarios where the flame is attached to the surface, the high-intensity radiation zone near the fire source is more tolerant of lower resolutions (e.g., 32-4), though far-field predictions remain sensitive. This research provides critical selection guidelines for angular discretization in wildfire radiation models.