Introduction to 3D Game Programming with DirectX.9.0 - F. D. Luna

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The following code snippet shows how to use this function:

Observe that first we must fill outFa OG ONT structure to describe the kind of font we want to create.M

9.1.2 DrawingTText

Note: Alternatively, youAcan use the D3DXCreateFont function to obtain a pointer to Ean ID3DXFont interface.

Once we have obtained a pointer to an ID3DXFont interface, drawing text is a simple matter of calling the ID3DXFont::DrawText method.

INT ID3DXFont::DrawText(

LPCSTR pString, INT Count, LPRECT pRect, DWORD Format, D3DCOLOR Color

);

pString—Pointer to the string to draw

Count—Number of characters in the string. We can specify –1 if the string is null terminating.

pRect—Pointer to a RECT structure that defines the area on the screen to which the text is to be drawn

Format—Optional flags that specify how the text should be formatted; see the SDK documentation for details.

Color—The text color

Example:

Team-Fly®

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9.1.3 Computing the Frames Rendered Per Second

The ID3DXFont and CFont samples for this chapter compute and display the frames rendered per second (FPS). This section explains how to compute the FPS.

First we instantiate the following three global variables:

We compute the FPS every one second; this gives us a good average. In addition, it keeps the FPS the same for one second, giving us enough time to read it before it changes again.

So every frame we increment FrameCnt and add the time elapsed from the last frame to TimeElapsed:

The DirectX SDK provides some useful utility code located in the \Samples\C++\Common folder of your DXSDK root directory. Among that code is the CD3DFont class, which renders text using textured triangles and Direct3D. Since CD3DFont uses Direct3D for rendering instead of GDI, it is much faster than ID3DXFont. However, CD3DFont does not support the complex fonts and formatting that

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ID3DXFont does. If you’re after speed and only need a simple font, the CD3DFont class is the way to go.

To use the CD3DFont class, you need to add the following files to your application: d3dfont.h, d3dfont.cpp, d3dutil.h, d3dutil.cpp, dxutil.h, and dxutil.cpp. These files can be found in the Include and Src folders located in the previously mentioned Common folder.

9.2.1 Constructing a CD3DFont

To create a CD3DFont instance, we simply instantiate it like a normal C++ object; below is the constructor prototype:

CD3DFont(const TCHAR* strFontName, DWORD dwHeight, DWORD

dwFlags=0L);

strFontName—A null-terminated string that specifies the typeface name of the font

dwHeight—The height of the font

dwFlags—Optional creation flags; you can set this parameter to zero or use a combination of the following flags; D3DFONT_BOLD,

D3DFONT_ITALIC, D3DFONT_ZENABLE.

After we have instantiated a CD3DFont object, we must call the following methods (in the order shown) that initialize the font:

Font = new CD3DFont("Times New Roman", 16, 0); // instantiate Font->InitDeviceObjects( Device ); Font->RestoreDeviceObjects();

9.2.2 Drawing Text

Now that we have constructed and initialized a CD3DFont object, we are ready to draw some text. Text drawing is done with the following method:

HRESULT CD3DFont::DrawText(FLOAT x, FLOAT y, DWORD dwColor,

const TCHAR* strText, DWORD dwFlags=0L);

x—The x-coordinate in screen space of where to begin drawing the text

y—The y-coordinate in screen space of where to begin drawing the text

dwColor—The color of the text

strText—Pointer to the string to draw

dwFlags—Optional rendering flags; you can set this parameter to 0 or use a combination of the following: D3DFONT_CENTERED,

D3DFONT_TWOSIDED, D3DFONT_FILTERED.

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Example:

Font->DrawText(20, 20, 0xff000000, “Hello, World”);

9.2.3 Cleanup

Before deleting a CD3DFont object, we must call some cleanup routines first, as the following code snippet illustrates:

Font->InvalidateDeviceObjects(); Font->DeleteDeviceObjects(); delete Font;

9.3 D3DXCreateText

This last function is used for creating 3D meshes of text. Figure 9.1 shows the 3D text mesh that the FontMesh3D sample of this chapter renders.

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Note: For your information only, the ID3DXMesh interface supports indexed triangle lists only as its primitive type.

Alternatively, if we just want to lock the buffers to read or write to them, we can use this next pair of methods. Note that these methods lock the entire vertex/index buffer.

HRESULT ID3DXMesh::LockVertexBuffer(DWORD Flags, BYTE** ppData);

HRESULT ID3DXMesh::LockIndexBuffer(DWORD Flags, BYTE** ppData);

The Flags parameter describes how the lock is done. Locking flags for a vertex/index buffer is explained in Chapter 3 where we first introduced buffers. The ppData argument is the address of a pointer that is to point to the locked memory when the function returns.

Remember to call the appropriate unlock method when you are done with the lock:

HRESULT ID3DXMesh::UnlockVertexBuffer();

HRESULT ID3DXMesh::UnlockIndexBuffer();

Below is a list of additional ID3DXMesh methods used to obtain geome- try-related information:

10.2 Subsets and the Attribute Buffer

A mesh consists of one or more subsets. A subset is a group of triangles in the mesh that can all be rendered using the same attribute. By attribute we mean material, texture, and render states. Figure 10.1 illustrates how a mesh representing a house may be divided into several subsets.

Figure 10.1: A house broken up into subsets

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We label each subset by specifying a unique positive integer value for that subset. This value can be any number that can be stored in a DWORD. For instance, in Figure 10.1 we labeled the subsets 0, 1, 2, and 3.

Each triangle in the mesh is given an attribute ID that specifies the subset in which the triangle lives. For example, from Figure 10.1, the triangles that make up the floor of the house would have an attribute ID of 0 to indicate that they live in subset 0. Similarly, the triangles that make up the walls of the house have an attribute ID equal to 1 to indicate that they live in subset 1.

The attribute IDs for the triangles are stored in the mesh’s attribute buffer, which is a DWORD array. Since each face has an entry in the attribute buffer, the number of elements in the attribute buffer is equal to the number of faces in the mesh. The entries in the attribute buffer and the triangles defined in the index buffer have a one-to-one correspondence; that is, entry i in the attribute buffer corresponds with triangle i in the index buffer. Triangle i is defined by the following three indices in the index buffer:

A= i 3

B= i 3 + 1

C= i 3 + 2

Figure 10.2 shows this correspondence:

Figure 10.2: The correspondence between the triangles defined in the index buffer and the entries in the attribute buffer. We see that triangle 0 exists in subset 0, triangle 1 exists in subset 4, and triangle n exists in subset 2.

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We can access the attribute buffer by locking it, as this next code snippet illustrates:

DWORD* buffer = 0;

Mesh->LockAttributeBuffer(lockingFlags, &buffer);

// Read or write to attribute buffer...

Mesh->UnlockAttributeBuffer();

10.3 Drawing