When working with 3D models in Unity, applying MTL files to OBJ models can greatly enhance the visual quality and realism of the rendering. Here are the steps to put MTL on OBJ in Unity:

1. Import the OBJ and MTL files into Unity: Start by importing the OBJ model and its corresponding MTL file into your Unity project. Unity supports the import of both OBJ and MTL files, making it easy to work with the materials and textures.

2. Apply the MTL to the OBJ material: Once the OBJ and MTL files are imported, you can apply the MTL file to the OBJ material in Unity's Inspector panel. Select the OBJ model in the hierarchy, then navigate to the Material section in the Inspector. From there, you can assign the MTL file to the material, which will link the texture and material properties to the OBJ model.

3. Adjust material properties: After applying the MTL file to the OBJ material, you can further adjust the material properties to achieve the desired look and feel for your 3D model. Unity provides a wide range of options for tweaking material properties such as color, shininess, transparency, and more. Experiment with these properties to fine-tune the appearance of your 3D model.

4. Test and refine: Once you have applied the MTL file to the OBJ material and adjusted the material properties, it's time to test the rendering in Unity. Use the Scene view or Game view to visualize how the model looks with the applied MTL file. Make any necessary refinements to the material properties to achieve the desired visual result.

5. Optimize for performance: Finally, it's important to consider performance optimization when working with MTL files and OBJ models in Unity. Depending on the complexity of the model and the texture quality, you may need to adjust settings such as texture resolution and texture compression to ensure smooth rendering performance.

By following these steps, you can effectively put MTL on OBJ in Unity to create stunning 3D visuals for your projects.