Free tools for baking texture atlases for 3D models include Blender (with native baking features), xNormal (specialized for texture map generation), and Krita (via texture baking plugins).
These tools transfer details from high-poly to low-poly models and combine maps (like normal or ambient occlusion) into a single atlas—ideal for game assets or real-time 3D projects.
If you’re new to atlasing, start with Blender: its integrated workflow and community tutorials simplify learning to bake and merge textures step-by-step.