3D 图形转换(3D Transformation)

1. 移动





图形学中，有以下几种空间概念： object space, world space, view space, projection space, 和 screen space

通常物品显示出来，需要经如下变换





旋转： 如下分别表示沿X,Y,Z 旋转





缩放变换：sx, sy, sz分别表示沿X,Y,Z的缩放因子





切换变换 Shearing









D3D 实现 思路

1.定义世界矩阵(world transformation)：

D3DXMATRIX matWorld;
D3DXMatrixRotationY( &matWorld, timeGetTime()/150.0f );
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

2.定义视图矩阵(View Transformation):

D3DXVECTOR3 vEyePt ( 0.0f, 3.0f,-5.0f );      // 定义 eye point
D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );    //  look-at  point
D3DXVECTOR3 vUpVec ( 0.0f, 1.0f, 0.0f );       // “up” direction
D3DXMATRIXA16 matView;
D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );   // 计算view Matrix
g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );

3. 定义投影矩阵(Projection Transformation): 把3D 物品投影到2D 屏幕

D3DXMATRIX matProj;
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f );   //  建立 projection Matrix， 1/4 pi 定义视野角度，后面的1,100 定义视锥远近
g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );

在D3D 中可以使用 XMMatrixRotationY(t) 表示绕自身Y轴旋转

以原点为中心，4 为半径，圆周运动

// 2nd Cube: Rotate around origin
XMMATRIX mSpin = XMMatrixRotationZ( -t );
XMMATRIX mOrbit = XMMatrixRotationY( -t * 2.0f );
XMMATRIX mTranslate = XMMatrixTranslation( -4.0f, 0.0f, 0.0f );
XMMATRIX mScale = XMMatrixScaling( 0.3f, 0.3f, 0.3f );
matWorld2 = mScale * mSpin * mTranslate * mOrbit;

// Update variables for the second cube //
ConstantBuffer cb2;
cb2.mWorld = XMMatrixTranspose(matWorld2 );
cb2.mView = XMMatrixTranspose( matView );
cb2.mProjection = XMMatrixTranspose( matProj );
g_pImmediateContext->UpdateSubresource( g_pConstantBuffer, 0, NULL, &cb2, 0, 0 );
//
// Render the second cube
//
g_pImmediateContext->DrawIndexed( 36, 0, 0 );