根据按键修改相机位置

Question

我有一个使用 DirectX 在屏幕上呈现图形的应用程序。第一人称的默认视图使用以下代码设置，将 Y 轴设置为 0。代码包含在 Render() 之前调用的 SetupCamera() 函数中。

 D3DXVECTOR3 vCamera(5.0f, 0.0f, -45.0f); 

我正在使用 DirectInput 来管理用户输入。我希望能够允许用户按 SPACE 并将 Y 轴值更改为 90 以切换到俯视图，然后再次按下将其切换回来。我目前在我的 ProcessKeyboardInput() 函数中有以下代码，在 Render() 之前调用。

if (KEYDOWN(buffer, DIK_SPACE))
{
  \\ ???    
}

但我不确定我需要做什么来允许用户调整不中断渲染的值。我必须在这里遗漏一些简单的东西。任何帮助将非常感激。谢谢！

完整的 CameraSetup() 代码...

void SetupCamera()
{
// Setup View Matrix
D3DXVECTOR3 vCamera(5.0f, 0.0f, -45.0f);    // camera location  x,y,z plane
D3DXVECTOR3 vLookat(5.0f, 5.0f, 0.0f);      // camera direction x,y,z plane
D3DXVECTOR3 vUpVector(0.0f, 1.0f, 0.0f);    // which way is up x,y,z plane
    D3DXMATRIX matView;
    D3DXMatrixLookAtLH( &matView, &vCamera, &vLookat, &vUpVector);
    D3D_Device -> SetTransform(D3DTS_VIEW, &matView);


 // Setup Projection Matrix to transform 2D geometry into 3D space
 D3DXMATRIX matProj;
     D3DXMatrixPerspectiveFovLH(&matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f);
     D3D_Device -> SetTransform(D3DTS_PROJECTION, &matProj);
}

完整的 ProcessKeyboardInput() 代码...

void WINAPI ProcessKeyboardInput()
{ 
// Define a macro to represent the key detection predicate
#define KEYDOWN(name, key) (name[key] & 0x80) 

// Create buffer to contain keypress data
char     buffer[256];
HRESULT  hr;

// Clear the buffer prior to use
ZeroMemory(&buffer, 256);

 hr = g_pDIKeyboardDevice -> GetDeviceState(sizeof(buffer),(LPVOID)&buffer); 
if FAILED(hr) 
{ 
    // If device state cannot be attained, check if it has been lost and try to      aquire it again
    hr = g_pDIKeyboardDevice -> Acquire();
    while (hr == DIERR_INPUTLOST) hr = g_pDIKeyboardDevice -> Acquire();

    hr = g_pDIKeyboardDevice -> GetDeviceState(sizeof(buffer),(LPVOID)&buffer); 
} 

bool topView = false;

if (KEYDOWN(buffer, DIK_Q))
{
    // 'Q' has been pressed - instruct the application to exit.
    PostQuitMessage(0);
}

if (KEYDOWN(buffer, DIK_SPACE))
{
    // Space has been pressed - swap from 1st person view to overhead view

    // topView is true
 topView = !topView;

 // if topView is true, adjust camera accordingly
 if (topView) 
    {
        vCamera.y = 90.f;
    } 
    else        // if untrue, set camera to 1st person
        {
            vCamera.y = 0.f;
        }

    }
}

Answer 1

我认为你在正确的轨道上。不要担心“中断渲染”。在任何图形应用程序中，渲染调用之间都会进行大量处理。像这样的东西怎么样：

// Have this somewhere appropriate in the code
bool topView = false;

if (KEYDOWN(buffer, DIK_SPACE))
{
    // Toggle top view
    topView = !topView;

    // Set camera vector
    if (topView) {
        vCamera.y = 90.f;
    } else {
        vCamera.y = 0.f:
    }
}

更新后，您需要再次将矩阵发送到 DirectX。基本上，既然vCamera（或任何其他视图向量）已更改，您需要再次调用以下代码块。我建议将代码捆绑在SetupCamera() 函数中，并在检查用户输入后在Render() 函数中调用它。这还需要将vCamera 等移出函数之外，以便其他函数可以使用它们。

// vCamera, vLookat, vUpVector defined outside function

// Call this in rendering loop to set up camera
void SetupCamera() {
    // Calculate new view matrix from view vectors
    D3DXMATRIX matView;
    D3DXMatrixLookAtLH( &matView, &vCamera, &vLookat, &vUpVector);
    D3D_Device -> SetTransform(D3DTS_VIEW, &matView);

    // Setup Projection Matrix to transform 2D geometry into 3D space
    D3DXMATRIX matProj;
    D3DXMatrixPerspectiveFovLH(&matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f);
    D3D_Device -> SetTransform(D3DTS_PROJECTION, &matProj);
}