I3D raster image file contains 3D textures used by computer animation software Houdini. The software was developed in Canada, and is used for creating and editing professional scenes with dynamic effects, lighting, and video composition.

Houdini offers wide array of funtions to generate complex physical phenomena, so I3D files are typically used for storing cloud and smoke image data. I3D document, however, can easily hold any volumetric data.