Image based or non-image based ray tracing algorithms are generally used to characterize indoor propagation channels, However, the existing models cannot efficiently cope with multiple reflected and/or transmitted ray fields, The optimal ray tracing model presented in this paper provides definite advantages in calculating the contributions of these rays, The proposed model is based on images, but it is optimum in the sense that only those rays which belong to the configuration space and hence contribute to the received signal are automatically singled out at the outset. Mathematical formulations of the optimal ray model are derived by the use of suitably defined auxiliary canonical problems. Then utilizing the asymptotic reduction of the corresponding Green's function representations, explicit expressions are derived, which for given transmitter/receiver locations allow one to determine all possible ray paths and the associated field constituents. Due to the improved computational efficiency, multiple reflected and/or transmitted ray fields can conveniently be traced in vector form. Signal fading and rms delay spread characteristics of idealized indoor propagation environments can be calculated accurately. The optimal ray model presented in this paper can therefore be used to generate benchmark solutions for assessing the loss of accuracy when depolarization effects are neglected or when the ray series is truncated prematurely.