Top: Illustration of the Hōkū interpolation process. The left panel shows the initial masses and ZAMS velocities of the grid models in purple and turquoise, and the simulated star is shown in red. The right panel shows the evolutionary models in a spectroscopic HR diagram and the interpolated effective temperature and spectroscopic luminosity of the simulated star. The crosses mark where the effective temperature and spectroscopic luminosity are interpolated from the grid models. Bottom: Resulting evolutionary track of the 27 M_⊙, $v_{\mathrm{ZAMS}}=200{\mathrm{km}\mathrm{s}}^{-1}$ interpolated star in a spectroscopic HR diagram, along with the grid models used for interpolation.