A computer-implemented method and system for navigation and display of 3D image data is described. In the method, a 3D image dataset to be displayed is retrieved and a highlight position is identified within the 3D image dataset. A scalar opacity map is calculated for the 3D image dataset, the opacity map having a value for each of a plurality of positions in the 3D image dataset, the respective value being dependent on the respective position relative to the highlight position, and on the value of the 3D image at the respective position relative to the value of the 3D image at the highlight position. The opacity is applied to the 3D image dataset to generate a modified 3D image view.