You can create new polygon components from existing ones using the Extrude feature (Edit Mesh > Extrude). When you extrude a polygon component (for example, a face, edge, or vertex), you create additional polygon components from the ones you selected. Using the Extrude feature you will:

• Create the lower front region of the helmet by extruding the polygon face you created in the last section of the lesson.
• Extrude edges around the face shield and along the lower bottom edge.

To extrude the polygon face for the lower front region

1. Enlarge the scene view to a single perspective view.
2. With the polygon face still selected, choose Edit Mesh > Extrude.

   The extrude manipulator appears on the selected face.

3. In the perspective view, drag the blue arrow on the manipulator to extrude a section of mesh out from the face (positive X) a distance of approximately one half a grid unit (see image).
   
4. Press the g key to extrude again.
5. Click the large circle that surrounds the manipulator to display the rotate manipulators and then drag the green circular manipulator to rotate the angle of the extrusion to match the angle in the reference sketch (see image) and then drag the arrow manipulator a second time to extrude a second section of mesh.
   Tip

   As you change the angle of rotation and extrude the mesh you can also momentarily switch between the move or scale manipulators to fine tune the position and scale of each section as you extrude it.

   
6. Press the g key once again and create a third extruded region using the manipulator to move, rotate, or scale the extruded segment of the mesh so you position it correctly when compared to the reference sketch (see image). You may also want to view the extrusion from either the top or front view to ensure your extrusion doesn’t extend outwards more than the side region.
   
7. Save your work.

To delete unwanted faces on the extruded mesh

1. Tumble the perspective view until you can view the inside of the lower front region (see image below).
2. Select the faces that appear on the inside of the mesh you just extruded, including the faces on either end of the extrusion.

   These faces were required for creating the extruded portions of the lower region but are not needed beyond this point.

3. Press the Delete key to delete the selected faces.
   

   When you are finished, a gap will exist between the last extruded segment of the lower region and the helmet mesh.

   

You’ll combine these separate meshes together and then create a mesh that bridges between them in the next section of the lesson. To prepare for the bridge, you need to extrude more edges on the helmet mesh so that the number of edges match when you create the bridge.

To extrude the bottom edges of the helmet mesh

1. In the perspective view, select the lower edges of the helmet mesh using Select > Select Border Edge Tool.
2. Select Edit Mesh > Extrude, then drag the blue arrow manipulator in a direction towards the inside of the helmet to create a row of edges that are perpendicular to the selected bottom edges. Extrude these edges a distance that is approximately one grid unit in depth (see image below).
   

To extrude top and side edges for the face shield

1. In the perspective view, select the upper and side edges on the helmet mesh using Select > Select Border Edge Tool (see image below).
2. Select Edit Mesh > Extrude and then drag the blue arrow on the extrude manipulator in a direction towards the inside of the helmet to create edges that are perpendicular to the top and side edges of the face shield. Extrude these edges a distance that is approximately one grid unit in depth (see image below).
   

To move vertices on the lower front region to match the reference sketch

1. In the perspective view, right-click on the helmet and select vertex mode to change the selection type to vertices.
2. Select the four vertices on the lower front region of the helmet that are near the axis of symmetry (see image below) and using the Move Tool, move the selected vertices upwards by dragging the green arrow on the Move Tool manipulator so that the lower front region of the helmet matches the reference sketches as they appear in the various orthographic views.
   
3. Adjust any vertices on the lower region that may require minor repositioning by selecting and moving them as necessary.