Platform SDK: DirectX

Step 3.3: Prepare the Geometry

[C++]

This section pertains only to application development in Visual Basic. See Direct3D Immediate Mode C/C++ Tutorials.

[Visual Basic]

The Triangle tutorial code initializes the geometry in the application-defined InitGeometry subroutine by defining four D3DVECTOR types; a vector type is used for each of the three points used to define the triangle, and for the one point used to define the normal in 3-D space. Technically, you are not required to set up the geometry at this time—you can do it anytime prior to calling the rendering methods:

Private Sub InitGeometry()
 
    ' Set up the geometry for the triangle.
    Dim p1 As D3DVECTOR, _
        p2 As D3DVECTOR, _
        p3 As D3DVECTOR, _
        vNormal As D3DVECTOR
   
    ' Set values for three points used to define a triangle.
    p1.x = 0#: p1.y = 5#: p1.z = 0#
    p2.x = 5#: p2.y = -5#: p2.z = 0#
    p3.x = -5#: p3.y = -5#: p3.z = 0#
    
    ' Create a normal vector--shared by the points of the
    ' triangle--that points toward the viewpoint. Note that
    ' we reverse the Z coordinate for the normal of the points
    ' that define the backside of the triangle.
    vNormal.x = 0#: vNormal.y = 0#: vNormal.z = -1#

The DirectX7.CreateD3DVertex method uses the members of a D3DVECTOR type to fill D3DVERTEX types by using the individual values that represent discrete vertex components. Fill the global D3DVERTEX type array, g_TriangleVert, with the triangle's vertex information:

 ' Create the 3 vertices for the front of the triangle.
    g_dx.CreateD3DVertex p1.x, p1.y, p1.z, vNormal.x, vNormal.y, vNormal.z, 0, 0, _
                         g_TriangleVert(0)
    g_dx.CreateD3DVertex p2.x, p2.y, p2.z, vNormal.x, vNormal.y, vNormal.z, 0, 0, _
                         g_TriangleVert(1)
    g_dx.CreateD3DVertex p3.x, p3.y, p3.z, vNormal.x, vNormal.y, vNormal.z, 0, 0, _
                         g_TriangleVert(2)
    
' Now do the same for the back of the triangle.
    g_dx.CreateD3DVertex p3.x, p3.y, p3.z, vNormal.x, vNormal.y, -vNormal.z, 0, 0, _
                         g_TriangleVert(3)
    g_dx.CreateD3DVertex p2.x, p2.y, p2.z, vNormal.x, vNormal.y, -vNormal.z, 0, 0, _
                         g_TriangleVert(4)
    g_dx.CreateD3DVertex p1.x, p1.y, p1.z, vNormal.x, vNormal.y, -vNormal.z, 0, 0, _
                         g_TriangleVert(5)

The preceding code fragment locates three points in 3-D space that define a triangle standing upright in the z=0 plane. After creating all the Direct3D-related objects, initializing the scene, and defining the geometry for your scene, you can render your scene as described in Step 4: Execute the Rendering Loop.