3ds max Polygon Modeling Extruding a planar surface to a closed volume And we're seeing a preview. And so what it's done is it's not created a new polygon. It's taken the existing polygon and shifted it backward and then it's created this new ring of polygons around that. But it's open. There's nothing in front here. We'll have to fix that. So okay this is what we want. We've got that so we can go ahead and click okay to complete the extrude polygons command and we want to flip the surface normals. Each one of these polygons has a direction and that is called its surface normal and we want those surface normals to be pointed outward so that when we view this from behind, it will look shaded. So let's see what that looks like. I'll tumble around or orbit around to the back. And we can se that these faces are pointed away from us because they're actually shaded black. So we want to flip all of those. The easy way to select all of those polygons is to select by element. Choose element sub-object mode and then click to select all those connected polygons and then click the flip button. You should do it from the modify panel here because I was having some issues with the modeling ribbon earlier so, just to be safe, we'll use the modify panel. Click the flip button and now the normals are reversed and if we orbit around to the front now, and exit out of element sub-object mode, now we see that the interior surfaces are rendering in black and this is what we want. The object is correctly oriented; the surface normals are all pointed outward and we can cover that hole just by adding a cap holes modifier
