Microsoft DirectX 9.0

Setting Up a Projection Matrix

The following ProjectionMatrix sample function sets the front and back clipping planes, as well as the horizontal and vertical field of view angles. This code parallels the approach discussed in the What Is the Projection Transformation? topic. The fields of view should be less than pi radians.

ProjectionMatrix(const float near_plane, // Distance to near clipping 
                                         // plane
                 const float far_plane,  // Distance to far clipping 
                                         // plane
                 const float fov_horiz,  // Horizontal field of view 
                                         // angle, in radians
                 const float fov_vert)   // Vertical field of view 
                                         // angle, in radians
    float    h, w, Q;

    w = (float)1/tan(fov_horiz*0.5);  // 1/tan(x) == cot(x)
    h = (float)1/tan(fov_vert*0.5);   // 1/tan(x) == cot(x)
    Q = far_plane/(far_plane - near_plane);

    D3DXMATRIX ret;
    ZeroMemory(&ret, sizeof(ret));

    ret(0, 0) = w;
    ret(1, 1) = h;
    ret(2, 2) = Q;
    ret(3, 2) = -Q*near_plane;
    ret(2, 3) = 1;
    return ret;
}   // End of ProjectionMatrix

After creating the matrix, set it with IDirect3DDevice9::SetTransform specifying D3DTS_PROJECTION.

The Direct3D extensions (D3DX) utility library provides the following functions to help you set up your projections matrix.

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