Ortho/Perspective matrices are different than from DirectX 9 Math library.

Hi there.
Currently i have working on some test and found some unclear moments between Mathfu and DirectX Math.
I know how the canonical perspective and orthographic matrices looks like. What i wondering is why DirectX Math uses different calculations for perspective and orthographic matrices?
I work with DirectX Math almost 10 years and never had a problems with projection matrices.

For example i had run tests from 'matrix_test.cpp' for DirectX 9 Math and get next results.
```
Right-handed perspective
   ( atan( 1.0 ) * 2.0, 1.0, -2.0, 2.0 )
        Mathfu              DirectX9
| 1.0  0.0  0.0  0.0 | 1.0  0.0  0.0  0.0 |
| 0.0  1.0  0.0  0.0 | 0.0  1.0  0.0  0.0 |
| 0.0  0.0 -0.5 -1.0 | 0.0  0.0 -0.5 -1.0 |
| 0.0  0.0  2.0  0.0 | 0.0  0.0  1.0  0.0 |

Left-handed perspective
   ( atan( 1.0 ) * 2.0, 1.0, -2.0, 2.0 )
        Mathfu              DirectX9
| 1.0  0.0  0.0  0.0 | 1.0  0.0  0.0  0.0 |
| 0.0  1.0  0.0  0.0 | 0.0  1.0  0.0  0.0 |
| 0.0  0.0  0.5  1.0 | 0.0  0.0  0.5  1.0 |
| 0.0  0.0  2.0  0.0 | 0.0  0.0  1.0  0.0 |

Right-handed orthographic
      ( 1.0, 3.0, 1.0, 3.0, 1.0, 3.0 )
        Mathfu              DirectX9
| 1.0  0.0  0.0  0.0 | 1.0  0.0  0.0  0.0 |
| 0.0  1.0  0.0  0.0 | 0.0  1.0  0.0  0.0 |
| 0.0  0.0 -1.0  0.0 | 0.0  0.0 -0.5  0.0 |
|-2.0 -2.0 -2.0  1.0 |-2.0 -2.0 -0.5  1.0 |

Left-handed orthographic
      ( 1.0, 3.0, 1.0, 3.0, 1.0, 3.0 )
        Mathfu              DirectX9
| 1.0  0.0  0.0  0.0 | 1.0  0.0  0.0  0.0 |
| 0.0  1.0  0.0  0.0 | 0.0  1.0  0.0  0.0 |
| 0.0  0.0  1.0  0.0 | 0.0  0.0  0.5  0.0 |
|-2.0 -2.0 -2.0  1.0 |-2.0 -2.0 -0.5  1.0 |
```

This moment is crucial in cross-platform development perspective. In fact, the DirectX math library is good enough for using it on Windows desktop systems. But for portability purposes we need another math library. And Mathfu looks good enough to use it on other systems.

But that difference mixes the cards. Does the different calculations makes the real difference in results?

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Ortho/Perspective matrices are different than from DirectX 9 Math library. #22

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Ortho/Perspective matrices are different than from DirectX 9 Math library. #22

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