If you're working on 3D modeling in Rhino and want to add more realistic textures to your OBJ models, attaching a material file is the way to go. Here's a simple step-by-step guide to help you through the process.

Step 1: Start by opening your OBJ file in Rhino. If you don't have an OBJ file yet, you can import one into Rhino using the 'Import' or 'Open' function.

Step 2: Once your OBJ file is open, go to the 'Materials' panel in Rhino. If you can't find the 'Materials' panel, you can enable it by going to the 'Panels' menu and selecting 'Materials'.

Step 3: In the 'Materials' panel, click on the 'Create Material' button to create a new material for your OBJ object.

Step 4: After creating a new material, you can adjust its properties such as color, transparency, and reflectivity. You can also add a texture to the material by clicking on the 'Texture' button within the material properties.

Step 5: When adding a texture, Rhino allows you to choose from a variety of file types including JPEG, PNG, or TIFF. Select the texture file you want to use, and Rhino will apply it to the material.

Step 6: Once you have adjusted the material properties and added a texture, you can now assign the material to your OBJ object. To do this, select the OBJ object in the viewport, and then drag and drop the material from the 'Materials' panel onto the object.

Step 7: Congratulations! You have successfully attached a material file to your OBJ object in Rhino. You can now see the texture applied to your object in the viewport.

By following these simple steps, you can easily enhance the appearance of your 3D models in Rhino by attaching material files to your OBJ objects. Experiment with different textures and material properties to achieve the desired look for your models.

In conclusion, adding material files to OBJ objects in Rhino is a straightforward process that can significantly improve the visual quality of your 3D models. Whether you're working on architectural visualization, product design, or any other 3D project, mastering this technique will take your renders to the next level.