1 terabyte sounds like an outlier, but typically texture maps are used as inputs to shading calculations. So it's not uncommon for hero assets in large-scale VFX movies to have more than 10 different sets of texture files that represent different portions of a shading model. For large assets, it may take more than fifty 4K-16K images to adequately cover the entire model such that if you were to render it from any angle, you wouldn't see the pixelation. And these textures are often stored as mipmapped 16 bit images so the renderer can choose the most optimal resolution at rendertime.
So that can easily end up being several hundred gigabytes of source image data. At rendertime, only the textures that are needed to render what's visible in the camera are loaded into memory and utilized, which typically ends up being a fraction of the source data.
Large scale terrains and environments typically make more use of procedural textures, and they may be cached temporarily in memory while the rendering process happens to speed up calculations
So that can easily end up being several hundred gigabytes of source image data. At rendertime, only the textures that are needed to render what's visible in the camera are loaded into memory and utilized, which typically ends up being a fraction of the source data.
Large scale terrains and environments typically make more use of procedural textures, and they may be cached temporarily in memory while the rendering process happens to speed up calculations