Step 3: Defining the Projection Transformation Matrix

The projection transformation matrix defines how geometry is transformed from 3-D view space to 2-D viewport space.

The following code fragment creates the projection transformation matrix and then sets the current projection transformation for the Microsoft?Direct3D?device.

D3DXMATRIX matProj;
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f );
g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );

The first step is to call D3DXMatrixPerspectiveFovLH to set up the projection matrix. The first parameter is a pointer to a D3DXMATRIX structure that is the result of the operation. The second parameter defines the field of view, which tells how objects in the distance get smaller. A typical field of view is 1/4 pi, which is what the sample uses. The third parameter defines the aspect ratio. The sample uses the typical aspect ratio of 1. The fourth and fifth parameters define the near and far clipping plane. This determines the distance at which geometry should no longer be rendered. The Matrices sample project has its near clipping plane set at 1 and its far clipping plane set at 100.

The next step is to call IDirect3DDevice9::SetTransform to apply the transformation to the Direct3D device. The first parameter accepted by IDirect3DDevice9::SetTransform tells Direct3D which transformation to set. This sample uses the D3DTS_PROJECTION flag to specify that the projection transformation should be set. The second parameter is a pointer to a matrix that is set as the current transformation.

For more information about projection transformations, see Projection Transformation.

This tutorial has shown you how to use matrices. Tutorial 4: Creating and Using Lights shows how to add lights to your scene for more realism.