// ... and use that value to create the projection matrix.
            projectionMatrix = Matrix.CreatePerspectiveFieldOfView(
                MathHelper.ToRadians(45.0f), aspectRatio, .01f, 100000000);

(I just changed the far plane)

There doesn't seem to be any info on this problem... Any ideas? Workarounds? I really do need such a large area.

Swordshock:

In layman's terms, you are trying to map the range [0, 1] onto [0.01, 10000000].  With floating point numbers, that is not going to work so well.  To make matters worse, the range [0, 1] uses a logarithmic scale.  Decrease the space between the near and far planes.

Better yet... keep the far plane the same and change you near plane to be something more reasonable.

I'd recommend reading the link below... 

http://www.sjbaker.org/steve/omniv/love_your_z_buffer.html

MissileControl:

Swordshock:

In layman's terms, you are trying to map the range [0, 1] onto [0.01, 10000000].  With floating point numbers, that is not going to work so well.  To make matters worse, the range [0, 1] uses a logarithmic scale.  Decrease the space between the near and far planes.

Better yet... keep the far plane the same and change you near plane to be something more reasonable.

Did I specifically suggest he move the near plane farther away?  I simply said to move the near and far planes closer together (which could be achieved by moving either the near or the far plane).  :-)

In addition to the suggestions already made, it is a known issue to the XNA team that the Unproject method has a bug.

Here's a link to the Microsoft Connect issue:https://connect.microsoft.com/feedback/ViewFeedback.aspx?FeedbackID=318306&SiteID=226