AutoCAD is a powerful tool for creating and manipulating 3D solid models. Viewing 3D solids in AutoCAD can be a complex task, but with the right techniques, you can easily navigate and visualize your models in 3D space. Here are some helpful tips for viewing 3D solids in AutoCAD:

1. Use the ViewCube: The ViewCube is a handy tool that allows you to rotate and orient your 3D model in AutoCAD. You can click and drag on the ViewCube to quickly change your viewpoint and navigate around your model.

2. Set up a 3D view: AutoCAD provides several preset 3D views that you can use to quickly change your perspective. These views include top, bottom, front, back, left, right, isometric, and more. You can find these views in the View tab under the 3D Views panel.

3. Adjust the visual style: AutoCAD offers different visual styles for displaying your 3D model, such as wireframe, hidden, shaded, and realistic. Experiment with these different visual styles to find the one that best suits your needs and helps you understand your 3D solid.

4. Use the Orbit tool: The Orbit tool allows you to rotate your 3D model freely in 3D space. You can access the Orbit tool by clicking on the ViewCube or using the Orbit button in the navigation bar.

5. Utilize the 3D gizmo: The 3D gizmo is a set of widgets that allows you to manipulate your 3D model in different ways, such as rotating, panning, and scaling. You can access the 3D gizmo by clicking on the Gizmo button in the navigation bar.

6. Take advantage of section planes: Section planes are helpful for visually cutting through your 3D model to see its internal structure. You can use the Section Plane tool to create a section plane and adjust its position to get a better understanding of your 3D solid.

By using these tips and techniques, you can effectively view and manipulate 3D solids in AutoCAD. Whether you're a beginner or an experienced user, understanding how to navigate and visualize 3D models is essential for creating accurate and detailed designs in AutoCAD.