I find that if I edit (in a separate application) a bitmap file being used as a texture, Rhino will only update it if - prior to the image editing in the separate app - it wasn’t adjusted with the Rhino material editor’s gamma and other grading controls. If it has been, Rhino will only update it (with Rhino-based grading adjustments) if the Rhino image grading controls are adjusted to a different setting - if they are then adjusted back to the grading settings used prior to the bitmap’s editing in the separate app, the pre-edited bitmap (as adjusted) is mapped to the object. This shortcoming persists even if the project is saved and reopened.