初学Direct X (2)
初学Direct X (2)
这一次要学习如何现实位图,尽管看过对双缓冲机制还有很多疑问,但是这并不阻碍我对他的入门了解
Direct3D提供了一个双重/后台缓冲区,在调用CreateDevice之时就有了。其运行机制就是,我们需要在其中一个缓冲区上绘制完所需要显示的一切,之后将这个缓冲区快速的复制到另一个缓冲区,因为后者的缓冲区被称为Front Buffer,显示器在刷新之时会直接从中取出数据以显示,而前者就称之为backbuffer
但是,还有一种buffer,是可供我们在内存中进行操作的,被称之为surface,也有离屏表面的称呼,后面的表面都指的是离屏表面
1. 使用表面的实例
初始化变量:
LPDIRECT3D9 d3d = NULL;
LPDIRECT3DDEVICE9 d3ddev = NULL;
LPDIRECT3DSURFACE9 backbuffer = NULL;
// 指向内存中的表面
LPDIRECT3DSURFACE9 surface = NULL;
1.1 Game_Init()
bool Game_Init(HWND hwnd)
{
//initialize Direct3D
d3d = Direct3DCreate9(D3D_SDK_VERSION);
if (d3d == NULL)
{
MessageBox(hwnd, "Error initializing Direct3D", "Error", MB_OK);
return false;
}
//set Direct3D presentation parameters
D3DPRESENT_PARAMETERS d3dpp;
d3d->GetAdapterDisplayMode(D3DADAPTER_DEFAULT,&dm);
ZeroMemory(&d3dpp, sizeof(d3dpp));
d3dpp.Windowed = FALSE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
d3dpp.BackBufferCount = 1;
d3dpp.BackBufferWidth = dm.Width;
d3dpp.BackBufferHeight = dm.Height;
d3dpp.hDeviceWindow = hwnd;
//create Direct3D device
d3d->CreateDevice(D3DADAPTER_DEFAULT,
D3DDEVTYPE_HAL, hwnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp, &d3ddev);
if (!d3ddev)
{
MessageBox(hwnd, "Error creating Direct3D device", "Error", MB_OK);
return false;
}
//set random number seed
// 用于Game_Run()
srand((unsigned int)time(NULL));
//clear the backbuffer to black
//注意这里并没有获取到backbuffer指针,就可以直接Clear backbuffer
d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);
//create pointer to the back buffer
//通常这是指向真实后台缓冲区的指针
d3ddev->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO, &backbuffer);
//create surface
HRESULT result = d3ddev->CreateOffscreenPlainSurface(
100, //width of the surface
100, //height of the surface
D3DFMT_X8R8G8B8, //surface format
D3DPOOL_DEFAULT, //memory pool to use
&surface, //pointer to the surface
NULL); //reserved (always NULL)
if (result != D3D_OK) return false;
return true;
}
这样一来,就获取了backbuffer的位置,并且创造了一个离屏表面,可供我们进行绘图操作
1.2 Game_Run()
void Game_Run(HWND hwnd)
{
//make sure the Direct3D device is valid
if (!d3ddev) return;
//start rendering
if (d3ddev->BeginScene())
{
//将离屏表面填色
int r = rand() % 255;
int g = rand() % 255;
int b = rand() % 255;
d3ddev->ColorFill(surface, NULL, D3DCOLOR_XRGB(r, g, b));
//把离屏表面复制到backbuffer
RECT rect;
rect.left = rand() % dm.Width;
rect.right = rect.left + rand() % (dm.Width - rect.left);
rect.top = rand() % dm.Height;
rect.bottom = rect.top + rand() % (dm.Height - rect.top);
d3ddev->StretchRect(surface, NULL, backbuffer, &rect, D3DTEXF_NONE);
//stop rendering
d3ddev->EndScene();
//将backbuffer的数据显示到屏幕上
d3ddev->Present(NULL, NULL, NULL, NULL);
}
//check for escape key (to exit program)
if (KEY_DOWN(VK_ESCAPE))
PostMessage(hwnd, WM_DESTROY, 0, 0);
}
1.3写到这里的时候我发现几个问题
1) 似乎无法操作front buffer?
这正是双缓冲的机制,因为直接操作front buffer会导致一些问题,想象一下,若屏幕的刷新频率很快,而此时你正在生成一个计算量巨大的数据,正在你计算之时,显示器已经来尝试取n次数据了,而这n次取出的图像都是一部分且不连贯的。故而出现了双缓冲技术,在backbuffer绘制好之后再将其显示在屏幕上
2)backbuffer和frontbuffer的是怎么运转的,好像只要调用Present就可以将backbuffer的显示在屏幕上了
2. 加载位图
需要使用d3dx,它是Direct3D Extensions 即Direct3D的扩展,需要进行如下的引用:
#include <d3dx9.h>
#pragma comment(lib,"d3dx9.lib")
有趣的就是D3DXLoadSurfaceFromFile函数了,他可以装载.bmp , .jpng, .png等一系列的位图,调用示例如下:
result = D3DXLoadSurfaceFromFile(
surface,
NULL,
NULL,
"show.png",
NULL,
D3DX_DEFAULT,
0,
NULL
);
3. 绘制表面
StretchRect函数可以将某个表面的一部分或全部位块传输到另一个表面
HRESULT StretchRect(
IDirect3DSurface9* pSourceSurface,
CONST RECT* pSourceRect,
IDirect3DSurface9* pDestSurface,
CONST RECT* pDestRect,
D3DTEXTUREFILTERTYPE Filter)
这里值得一提的是,若rect超出了pDestSurface的显示范围,函数还是可以正常运行的,下面是调用示例:
d3ddev->StretchRect(surface, NULL, backbuffer, &rect, D3DTEXF_NONE);