Three dimensional [3D] image data and auxiliary graphical data are combined for rendering on a 3D display (30) by detecting depth values occurring in the 3D image data, and setting auxiliary depth values for the auxiliary graphical data (31) adaptively in dependence of the detected depth values. The 3D image data and the auxiliary graphical data at the auxiliary depth value are combined based on the depth values of the 3D image data. First an area of attention (32) in the 3D image data is detected. A depth pattern for the area of attention is determined, and the auxiliary depth values are set in dependence of the depth pattern.