Use TexturePacker3D to combine model textures into atlases. Or extract models from atlases — both is possible!

Features:

• Combine your 3d models textures into texture atlases. Automatically combine the textures of your 3d models in shared atlases to reduce memory usage and speed up rendering. Choose the number of output textures and sizes. Automatically scale textures to fit your constraints.
• Consolidate and optimize your 3d models. TexturePacker3D lets you consolidate Textures used in a model into one texture atlas — or more if needed. You can also extract the required textures of a model if it uses a shared texture atlas.