Extruding a planar surface to a closed volume

- [Instructor] The monitored glass…at the front of the monitor here…is a perfectly flat plane with no thickness.…And I want to give it some thickness…so that it will render with physical accuracy.…And we can do that,…but we have to jump through…a couple of extra hoops to make it happen.…I'll select that monitor glass object…and then isolate the selection.…Click on isolate selection,…and then get in very close in the lower right corner.…I want to be able to see this.…We're only going to extrude this a very small amount.…

Then we can go into polygon subobject mode…from the modify panel or from the modeling ribbon,…and then we can do our extrude command.…One way to access the caddy for that…is to click on the options box in the modify panel,…and we get the extrude polygons caddy,…and we want to give this a very low negative value.…So in the amount field type in -0.3 cm,…press enter,…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…