Top: illustration of the interpolation procedure of STARMAKER in the 3_ZAMS – m_i plane. Individual model sequences are indicated by filled circles. Red lines indicate lines of constant mass. In this example, the properties of a star with initial mass M_i = 18 M_⊙ and initial velocity 3_ZAMS = 240 km   s^-1are determined through interpolation (the intersection of the blue dashed lines). starmaker chooses the circled models when interpolating. Models marked by triangles would be chosen if the nearest neighbor method was used. Black arrows indicate the sequence of the interpolation, as described in the text. Dashed lines are intended as guide to the eye to distinguish models of similar velocity. Bottom: interpolated track (red crosses), resulting from the example given above. The over plotted full blue line shows the model calculated with our stellar evolution code. The four black lines show the evolutionary tracks from which the model has been interpolated.