Drawing sprites messes up my model in XNA4

Question

I have a model which draws correctly in XNA4.

However if I try to add a background image (or any sprite), the rendering of my model is messed up. There are two problems with the rendering

1. model is partially transparent
2. hidden surfaces are visible.

Above is the 'problem' rendering (the cyan coloured cockpit cover is visible through the bottom of the ship)

This is how the rendering should look

Answer 1

The problem is caused by the SpriteBatch.Begin() changing some of the rendering states.

This problem is solved in XNA 3.1 and earlier by using the SaveState flag (see this answer).

However in XNA 4.0+ you need to restore the state yourself.

Insert the following code after your sprite drawing but before your model drawing (or 3D primitive drawing)

GraphicsDevice.BlendState = BlendState.Opaque;
GraphicsDevice.DepthStencilState = DepthStencilState.Default;

Information based on original article by Shawn Hargreaves