Multipath Path Reflection

Description

Generates a reflected geometric path for a platform based on its original path definition and a single, infinite reflection plane defined by the equation ax + by + cz + d = 0. This mechanism is used internally by the simulation framework to create the geometry for "dual" objects (representing reflected transmitters or receivers) needed for simulating single-bounce multipath interactions using the image method.

Assumptions

• Assumes the defined MultipathSurface accurately represents a perfectly flat, infinite geometric plane suitable for specular reflection calculations.
• Assumes the core reflection logic (MultipathSurface::reflectPoint, using a precomputed reflection matrix) correctly implements a standard affine transformation for specular reflection of 3D points and vectors.
• Assumes the original positional path being reflected is defined using waypoints (<positionwaypoint>) and a supported interpolation type (e.g., static, linear, cubic), not using the Python-based path definition (<pythonpath>).
• Assumes the method for reflecting platform orientation – which involves converting the orientation to a Cartesian direction vector, reflecting that vector using reflectPoint, and converting the reflected vector back to an orientation representation (e.g., Elevation/Azimuth) – accurately represents the physical reflection of the platform's pointing direction.
• Assumes the reflection transformation applies correctly and independently to individual path waypoints (for Path and RotationPath) or to the starting parameters (for fixed-rate RotationPath).
• Assumes the reflection power scaling factor (_factor) associated with the MultipathSurface is stored correctly and applied appropriately during subsequent power calculations (e.g., in solveRe) to model reflection losses, separate from this geometric path generation.

Limitations

• Python Path Incompatibility: Cannot reflect positional paths that are defined using external Python scripts (<pythonpath>). An attempt to reflect such a path will result in a runtime error.
• Geometric Idealization: The reflection calculation is purely geometric, modeling perfect specular reflection off an infinite, perfectly smooth plane. It does not inherently account for real-world effects such as diffuse scattering, surface roughness, edge diffraction, absorption losses beyond the simple _factor, or the finite size of reflecting surfaces.
• Configuration Dependency: The accuracy of the generated reflected path is entirely dependent on the correct definition of the plane coefficients (a, b, c, d) provided in the XML configuration for the MultipathSurface.
• Waypoint/Parameter-Based Reflection: The reflection process operates primarily on the defined waypoints or starting parameters of the original path. It then assumes the standard interpolation method (e.g., linear, cubic) applies between these reflected points. This doesn't inherently model continuous interaction or curvature effects related to the surface during the interpolation interval itself, which could be relevant for highly dynamic scenarios or curved paths near the surface.
• Factor Affects Power Only: The reflection _factor stored in MultipathSurface is intended solely to influence power calculations downstream (simulating reflection loss). It does not alter the calculated geometry of the reflected path itself.

Related Components

• MultipathSurface class (defines the reflection plane geometry and the reflection power factor)
• Path::reflectPath method (logic for reflecting positional paths defined by waypoints)
• RotationPath::reflectPath method (logic for reflecting rotational paths)
• MultipathSurface::reflectPoint method (core geometric point/vector reflection using a matrix)
• Platform Motion (overall context for path definitions)
• Multipath Model (specifically Multipath Image Object Generation, which uses this reflected path)
• Simulation Logic (specifically Simulation of Reflected Paths via Duals and Reflection Factor Application)
• World::processMultipath (typically where the reflection process is initiated during setup)

Validation Status

• Needs Verification: The correctness and robustness of the path reflection implementation require dedicated validation, especially concerning orientation and interpolation effects.
• Key Areas for Validation:
  • Geometric accuracy of MultipathSurface::reflectPoint for various plane orientations and input points/vectors.
  • Correct transformation of positional waypoints and subsequent interpolation behavior along the reflected path.
  • Correctness and potential edge cases (e.g., angles near +/- pi/2 for elevation, wrapping behavior for azimuth) of the orientation reflection logic, particularly the conversions between orientation coordinates and Cartesian vectors.
  • Verification that attempting to reflect a Python-defined positional path reliably triggers an error.
  • Confirmation that the reflection factor (_factor) is not applied during geometric path generation but is applied correctly (typically only once for a single bounce) in power calculations involving dual objects (cross-reference with Reflection Factor Application).
  • Behavior when a path point lies exactly on the reflection plane or crosses it.
• Priority: High (Due to geometric complexity, the indirect way orientation is handled, potential for subtle errors in interpolation post-reflection, and its fundamental role in the accuracy of multipath simulation results).