How to draw 3d diagram in autocad?

1. Launch AutoCAD and set up your drawing area.
2. Go to the Home ribbon and select the Isometric Plane icon. This will set up your drawing environment in an isometric view, allowing you to draw 3-D objects easier.
3. Select the Line tool from the Draw ribbon and draw some 3-D shapes in your drawing area. You may need to play with the settings such as snap mode and ortho mode to make sure the lines are drawn accurately.
4. When you have finished drawing the shapes, use the Extrude tool from the Modify ribbon to turn them into 3-D objects.
5. If necessary, you can also add additional colours or materials to the 3-D objects you have created.
6. Finally, you can use the Orbit tool from the View ribbon to rotate and view your 3-D object from different angles.