Faces turning invisible

So ive made a model for putting into the game, however whenever i start the game engine the faces vanish so that im only able to see those that are on the side furthest away from the camera. Does anyone know how to correct this issue?

hi, in edit mode select all the faces and press W then select flip normals, from the menu.

If it is a solid object you can just press control N with all faces selected, that will recalculate the normals to face outward

If what The Oracle said doesn’t work, check the clipping on the camera. Select the camera and go to the Editing tab (F9) and play with the Clipping Start/End values.

Instead of flipping the normals, recalculate them to face outside with ctrl-n. That will make sure all normals are facing outwards.

If you just flip them, the ones that may correctly be facing outside would then be facing inside.

Yes but only on a solid mesh. I have had trees made with lots of planes, I hit control N and it turned the trunks inside out.