AutoCAD is a powerful tool for 2D and 3D design and modeling, but it can sometimes be challenging to work with different file formats. OBJ files are commonly used for 3D modeling and are supported by many design software. If you want to incorporate OBJ files into your AutoCAD projects, here are the steps to open OBJ in AutoCAD:

1. Open AutoCAD: Launch the AutoCAD software on your computer and ensure that you have a new or existing 3D modeling project open.

2. Import the OBJ File: In the AutoCAD interface, go to the 'Insert' tab and select 'Import.' Choose the OBJ file that you want to open and click 'Open' to import it into the AutoCAD project.

3. Adjust Scale and Position: Once the OBJ file is imported, you may need to adjust its scale and position to fit with the rest of your project. Use the scaling and positioning tools in AutoCAD to make the necessary adjustments.

4. Edit and Modify: With the OBJ file now part of your AutoCAD project, you can start editing and modifying it as needed. Use the various tools and features in AutoCAD to make changes to the OBJ file and integrate it seamlessly into your design.

5. Save and Export: After working with the OBJ file in AutoCAD, make sure to save your project to retain the changes. When you're ready to export the project, you can use the 'Export' feature to save it as a DWG or other compatible file format.

By following these steps, you can effectively open and work with OBJ files in AutoCAD for your 3D modeling and design projects. Incorporating OBJ files into your AutoCAD workflow allows you to take advantage of the diverse range of 3D modeling assets available in this format and enhance your design capabilities.