1. A method, comprising: performing via a computer: rendering an image document having a specified resolution, wherein the image document is rendered as a single two-dimensional (2D) image from a plurality of layers that are composited together, wherein each layer of the plurality of layers contains information that is different from other layers of the plurality of layers and each layer of the plurality of layers is editable independently of other layers of the plurality of layers, wherein a computer-generated three-dimensional (3D) model is rendered as one of the layers, and wherein one or more of the other layers comprise 2D artwork for the document separate from the 3D model; in response to input received during a 3D editing mode, manipulating the computer-generated three-dimensional (3D) model, wherein the computer-generated 3D model comprises a description of one or more 3D objects, wherein the description comprises geometry information for one or more surfaces of each 3D object; in response to said manipulating, rendering, from the 3D model, the one layer of the plurality of layers independently of other layers of the plurality of layers, and wherein during the 3D editing mode the one layer is rendered from the 3D model at a resolution lower than the specified resolution and within a single image tile; and subsequent to exiting the 3D editing mode, rendering the one layer from the 3D model at the specified resolution as a plurality of image tiles and compositing the one layer with the other layers of the plurality of layers.