Apply Matrix3D transformation to a 2D point in Silverlight

A third party algorithm that I'm using is creating the following matrix

|   355,78 :   -12,33 :    ,02 :    ,02 |
|    39,69 :   378,26 :    ,08 :    ,08 |
|  -145,43 :   -61,32 :   -,49 :   -,49 |
| 75610,61 : 25380,20 : 385,12 : 386,92 |

Which places the FrameworkElement in the correct place if I use it as a projection:

player.Graphic.Projection = new Matrix3DProjection { ProjectionMatrix = m };

But this also rotates and skews the element and I only need to move the element to the correct 2D coordinates.

I'm using the following code which I found here: http://www.gamespp.com/tutorials/matrixTransformationTutorial04.html

double x0 = 100, y0 = 100, z0 = 0;
var x1 = x0 * m.M11 + y0 * m.M12 + z0 * m.M13 + m.OffsetX;
var y1 = x0 * m.M21 + y0 * m.M22 + z0 * m.M23 + m.OffsetY;

z0 is unnecessary since it's always zero but I left it there just in case.

That produces x1=109954,75 and y1=67175,64 which are obviously wrong. It should generate some开发者_运维百科thing similar to mx=298 and my=162 (This is the mouse position when the projection was applied)

How can you transform X,Y coordinates using a Matrix3D?

Thanks