Production Designers consider the script/treatment, and any other form of brief, when producing the original designs. In the early stages of a project they will use the appropriate technique to demonstrate the proposed designs. For most types of animation, even CGI, designs are often developed initially in a 2D format and presented as drawings or paintings.
On some smaller productions, the Production Designer’s role may be combined with that of Art Director. This means an ongoing involvement with the project. They may also function as the Character Designer and/or Background Designer. Either alone or with a team, they will establish the environments, characters, props, colour schemes and any other design elements required for the production.
The amount of work required from Production Designers will vary depending upon the production and the size of the Art Department. On some projects, the Production Designer may also be the creative head of the Art Department. In this case they will supervise the work of a team which may include art directors, concept artists, character designers, sculptors, prop designers, background artists, set designers, model makers, set builders, set dressers and pre-vis (pre-visualisation) artists. 
In some cases, Production Designers will be commissioned to produce only key designs that define the style of the film and this work will be implemented and supervised throughout production by Art Directors. (Source: Hive)