Texturing - Introduction to 3D Game Programming with DirectX 9.0 - page 119

We begin by instantiating several global variables; one is the vertex
buffer that stores the vertices of the quad and the other is the texture
that we map to the quad:
IDirect3DVertexBuffer9* Quad = 0;
IDirect3DTexture9* Tex = 0;
The Setup routine is fairly straightforward; we construct a quad from
two triangles with texture coordinates defined. We then load the bitmap
file dx5_logo.bmp into an IDirect3DTexture9 interface. Next we
enable the texture using the SetTexture method. Finally, we set the
minification and magnification filters to linear filtering, and we also set
the mipmap filter to D3DTEXF_POINT :
bool Setup()
{
Device->CreateVertexBuffer(
6 * sizeof(Vertex),
D3DUSAGE_WRITEONLY,
Vertex::FVF,
D3DPOOL_MANAGED,
&Quad,
0);
Vertex* v;
Quad->Lock(0, 0, (void**)&v, 0);
// quad built from two triangles, note texture coordinates:
v[0] = Vertex(-1.0f, -1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);
v[1] = Vertex(-1.0f, 1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f);
v[2] = Vertex( 1.0f, 1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);
v[3] = Vertex(-1.0f, -1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);
v[4] = Vertex( 1.0f, 1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);
v[5] = Vertex( 1.0f, -1.0f, 1.25f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f);
Quad->Unlock();
// Load texture data.
D3DXCreateTextureFromFile(
Device,
"dx5_logo.bmp",
&Tex);
// Enable the texture.
Device->SetTexture(0, Tex);
// Set texture filters.
Device->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
Device->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
Device->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_POINT);
// set projection matrix
D3DXMATRIX proj;
D3DXMatrixPerspectiveFovLH(