I worked on concept development renders for Starbucks essentially since I started working onsite at Pepsico. There were always new flavors and types of packaging in the works. Renders would be needed in the early stages for product development. I created the Tetrapaks below essentially from photos taken of blank cartons (far left). Using traditional Photoshop retouching methods, I was able to take a concept mechanical and apply it to the photographed base packaging. Predominantly front views were used, but I also created a three-quarter view in the cases where it was requested.
Sometimes just taking a photo of a base image and retouching the concept artwork on it quite simply would not work. Most mechanical dies also held the schematic for the actual packaging in it; in this case, a plastic bottle. For the 40 ounce Iced Espresso Classics, I took the schematic, took one half of its outline path, closed the path. I then brought the half object into Photoshop and "lathed" it with its 3D functions. I then took the schematic, grooves and all. to create solid objects. From there I used blend modes to simulate the "swirls" you would see on the actual in-store product. Here is one example of dozens I was asked to do over the years. Occasionally, I would have to place them in cardboard trays, to simulate how they would be distributed.
In addition to concept work, I eventually handled photo-retouching for Starbucks. Below are some before and after images.