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ALPHA混合示例

2016-06-20 00:00 232 查看
技巧如下:

设置可变顶点格式时增加一个
D3DCOLOR类型的漫反射分量,其中的alpha值指定了alpha混合因子。

//
The 2D vertex format and descriptor

typedef
struct

{

float
x, y, z;
//
2D coordinates

float
rhw;
//
rhw

D3DCOLOR diffuse;
//
diffuse color component

} VERTEX;

#define
VERTEX_FVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)

//
initialize vertex data

VERTEX verts[]
=
{
{
100.0f
,
100.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
300.0f
,
100.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
100.0f
,
300.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
300.0f
,
300.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
50.0f
,
150.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
350.0f
,
150.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
50.0f
,
350.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
350.0f
,
350.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) }
};

D3DCOLOR类型可以用
D3DCOLOR_RGBA宏来生成,定义如下:

//
maps unsigned 8 bits/channel to D3DCOLOR

#define
D3DCOLOR_ARGB(a,r,g,b) \

((D3DCOLOR)((((a)
&
0xff
)
<<
24
)
|
(((r)
&
0xff
)
<<
16
)
|
(((g)
&
0xff
)
<<
8
)
|
((b)
&
0xff
)))

#define
D3DCOLOR_RGBA(r,g,b,a) D3DCOLOR_ARGB(a,r,g,b)

其中的a指定了alpha因子,a为255表示该颜色完全不透明,a为0表示该颜色完全透明。

在绘制的时候,将首先绘制的图形设置为禁用alpha混合模式,将后面绘制的图形设置为启用alpha混合模式,并设置alpha混合具体模式。

//
disable alpha blending and draw 2 polygons

g_d3d_device
->
SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
g_d3d_device
->
DrawPrimitive(D3DPT_TRIANGLESTRIP,
0
,
2
);

//
enable alpha blending and draw 2 polygons

g_d3d_device
->
SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_d3d_device
->
SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_d3d_device
->
SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
g_d3d_device
->
DrawPrimitive(D3DPT_TRIANGLESTRIP,
4
,
2
);

完整源码如下:

/*
**************************************************************************************
PURPOSE:
Alpha blending Demo

Required libraries:
D3D9.LIB
**************************************************************************************
*/

#include
<
windows.h
>

#include
<
stdio.h
>

#include
"
d3d9.h
"

#pragma comment(lib,
"
d3d9.lib
"
)

#define
WINDOW_WIDTH 400

#define
WINDOW_HEIGHT 400

#define
Safe_Release(p) if((p)) (p)->Release();

//
window handles, class and caption text.

HWND g_hwnd;
HINSTANCE g_inst;

static

char
g_class_name[]
=

"
AlphaClass
"
;

static

char
g_caption[]
=

"Alpha Blending Demo
"
;

//
the Direct3D and device object

IDirect3D9
*
g_d3d
=
NULL;
IDirect3DDevice9
*
g_d3d_device
=
NULL;

//
The 2D vertex format and descriptor

typedef
struct

{

float
x, y, z;
//
2D coordinates

float
rhw;
//
rhw

D3DCOLOR diffuse;
//
diffuse color component

} VERTEX;

#define
VERTEX_FVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)

IDirect3DVertexBuffer9
*
g_vertex_buffer
=
NULL;
IDirect3DTexture9
*
g_texture
=
NULL;

//
--------------------------------------------------------------------------------

//
Window procedure.

//
--------------------------------------------------------------------------------

long
WINAPI Window_Proc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{

switch
(msg)
{

case
WM_DESTROY:
PostQuitMessage(
0
);

return

0
;
}

return
(
long
) DefWindowProc(hwnd, msg, wParam, lParam);
}

//
--------------------------------------------------------------------------------

//
Initialize d3d, d3d device, vertex buffer, texutre.

//
--------------------------------------------------------------------------------

BOOL Do_Init()
{
D3DPRESENT_PARAMETERS present_param;
D3DDISPLAYMODE display_mode;
BYTE
*
vertex_ptr;

//
initialize vertex data

VERTEX verts[]
=
{
{
100.0f
,
100.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
300.0f
,
100.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
100.0f
,
300.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
300.0f
,
300.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
0
,
64
,
128
,
255
) },
{
50.0f
,
150.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
350.0f
,
150.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
50.0f
,
350.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) },
{
350.0f
,
350.0f
,
1.0f
,
1.0f
, D3DCOLOR_RGBA(
128
,
0
,
0
,
128
) }
};

//
do a windowed mode initialization of Direct3D

if
((g_d3d
=
Direct3DCreate9(D3D_SDK_VERSION))
==
NULL)

return
FALSE;

//
retrieves the current display mode of the adapter

if
(FAILED(g_d3d
->
GetAdapterDisplayMode(D3DADAPTER_DEFAULT,
&
display_mode)))

return
FALSE;

ZeroMemory(
&
present_param,
sizeof
(present_param));

//
initialize d3d presentation parameter

present_param.Windowed
=
TRUE;
present_param.SwapEffect
=
D3DSWAPEFFECT_DISCARD;
present_param.BackBufferFormat
=
display_mode.Format;

//
creates a device to represent the display adapter

if
(FAILED(g_d3d
->
CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, g_hwnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&
present_param,
&
g_d3d_device)))

return
FALSE;

//
create the vertex buffer and set data

g_d3d_device
->
CreateVertexBuffer(
sizeof
(VERTEX)
*

8
,
0
, VERTEX_FVF, D3DPOOL_DEFAULT,
&
g_vertex_buffer, NULL);

//
locks a range of vertex data and obtains a pointer to the vertex buffer memory

g_vertex_buffer
->
Lock(
0
,
0
, (
void
**
)
&
vertex_ptr,
0
);

memcpy(vertex_ptr, verts,
sizeof
(verts));

//
unlocks vertex data

g_vertex_buffer
->
Unlock();

return
TRUE;
}

//
--------------------------------------------------------------------------------

//
Release all d3d resource.

//
--------------------------------------------------------------------------------

BOOL Do_Shutdown()
{
Safe_Release(g_vertex_buffer);
Safe_Release(g_d3d_device);
Safe_Release(g_d3d);

return
TRUE;
}

//
--------------------------------------------------------------------------------

//
Render a frame.

//
--------------------------------------------------------------------------------

BOOL Do_Frame()
{

//
clear device back buffer

g_d3d_device
->
Clear(
0
, NULL, D3DCLEAR_TARGET, D3DCOLOR_RGBA(
0
,
0
,
0
,
255
),
1.0f
,
0
);

//
Begin scene

if
(SUCCEEDED(g_d3d_device
->
BeginScene()))
{

//
set the vertex stream, shader, and texture.

//
binds a vertex buffer to a device data stream

g_d3d_device
->
SetStreamSource(
0
, g_vertex_buffer,
0
,
sizeof
(VERTEX));

//
set the current vertex stream declation

g_d3d_device
->
SetFVF(VERTEX_FVF);

//
assigns a texture to a stage for a device

g_d3d_device
->
SetTexture(
0
, g_texture);

//
disable alpha blending and draw 2 polygons

g_d3d_device
->
SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
g_d3d_device
->
DrawPrimitive(D3DPT_TRIANGLESTRIP,
0
,
2
);

//
enable alpha blending and draw 2 polygons

g_d3d_device
->
SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_d3d_device
->
SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_d3d_device
->
SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
g_d3d_device
->
DrawPrimitive(D3DPT_TRIANGLESTRIP,
4
,
2
);

//
end the scene

g_d3d_device
->
EndScene();
}

//
present the contents of the next buffer in the sequence of back buffers owned by the device

g_d3d_device
->
Present(NULL, NULL, NULL, NULL);

return
TRUE;
}

//
--------------------------------------------------------------------------------

//
Main function, routine entry.

//
--------------------------------------------------------------------------------

int
WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR cmd_line,
int
cmd_show)
{
WNDCLASSEX win_class;
MSG msg;

g_inst
=
inst;

//
create window class and register it

win_class.cbSize
=

sizeof
(win_class);
win_class.style
=
CS_CLASSDC;
win_class.lpfnWndProc
=
Window_Proc;
win_class.cbClsExtra
=

0
;
win_class.cbWndExtra
=

0
;
win_class.hInstance
=
inst;
win_class.hIcon
=
LoadIcon(NULL, IDI_APPLICATION);
win_class.hCursor
=
LoadCursor(NULL, IDC_ARROW);
win_class.hbrBackground
=
NULL;
win_class.lpszMenuName
=
NULL;
win_class.lpszClassName
=
g_class_name;
win_class.hIconSm
=
LoadIcon(NULL, IDI_APPLICATION);

if
(
!
RegisterClassEx(
&
win_class))

return
FALSE;

//
create the main window

g_hwnd
=
CreateWindow(g_class_name, g_caption, WS_CAPTION
|
WS_SYSMENU,
0
,
0
,
WINDOW_WIDTH, WINDOW_HEIGHT, NULL, NULL, inst, NULL);

if
(g_hwnd
==
NULL)

return
FALSE;

ShowWindow(g_hwnd, SW_NORMAL);
UpdateWindow(g_hwnd);

//
initialize game

if
(Do_Init()
==
FALSE)

return
FALSE;

//
start message pump, waiting for signal to quit.

ZeroMemory(
&
msg,
sizeof
(MSG));

while
(msg.message
!=
WM_QUIT)
{

if
(PeekMessage(
&
msg, NULL,
0
,
0
, PM_REMOVE))
{
TranslateMessage(
&
msg);
DispatchMessage(
&
msg);
}

//
draw a frame

if
(Do_Frame()
==
FALSE)

break
;
}

//
run shutdown function

Do_Shutdown();

UnregisterClass(g_class_name, inst);

return
(
int
) msg.wParam;
}

效果图:

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