Medical image rendering method and apparatus

A medical image processing apparatus comprises processing circuitry configured to: obtain volumetric medical imaging data comprising a voxel value; obtain an opacity value corresponding to the voxel value; obtain an extinction color and/or transmission color corresponding to the voxel value; modify the extinction color and/or transmission color using the opacity value, wherein the modifying of the extinction color and/or transmission color is performed using a combined opacity model that combines a first opacity model and a second, different opacity model, such that the first opacity model makes a higher contribution to the modifying than the second opacity model at lower values of opacity, and the second opacity model makes a higher contribution to the modifying than the first opacity model at higher values of opacity; and render the volumetric medical imaging data using the modified extinction color and/or transmission color.