2012-04-24 327 views
1

我有一個方形區域,我必須確定鼠標指向的位置。
隨着D3DXIntersectTri我可以告訴如果鼠標指向它,但我無法計算x,y,z座標。從D3DXIntersectTri獲取世界座標

從頂點緩衝區中的圖,它與頂點數組初始化:

vertices[0].position = D3DXVECTOR3(-10, 0, -10); 
vertices[1].position = D3DXVECTOR3(-10, 0, 10); 
vertices[2].position = D3DXVECTOR3(10, 0, -10); 
vertices[3].position = D3DXVECTOR3(10, 0, -10); 
vertices[4].position = D3DXVECTOR3(-10, 0, 10); 
vertices[5].position = D3DXVECTOR3(10, 0, 10); 

我有這樣的方法,到目前爲止,這是不是給我正確的座標(僅適用於該區域的一小部分,接近兩個邊緣,內部的準確度更低):

BOOL Area::getcoord(Ray& ray, D3DXVECTOR3& coord) 
{ 
    D3DXVECTOR3 rayOrigin, rayDirection; 
    rayDirection = ray.direction; 
    rayOrigin = ray.origin; 

    float d; 

    D3DXMATRIX matInverse; 
    D3DXMatrixInverse(&matInverse, NULL, &matWorld); 

    // Transform ray origin and direction by inv matrix 
    D3DXVECTOR3 rayObjOrigin,rayObjDirection; 

    D3DXVec3TransformCoord(&rayOrigin, &rayOrigin, &matInverse); 
    D3DXVec3TransformNormal(&rayDirection, &rayDirection, &matInverse); 
    D3DXVec3Normalize(&rayDirection,&rayDirection); 

    float u, v; 
    BOOL isHit1, isHit2; 

    D3DXVECTOR3 p1, p2, p3; 
    p1 = vertices[3].position; 
    p2 = vertices[4].position; 
    p3 = vertices[5].position; 

    isHit1 = D3DXIntersectTri(&p1, &p2, &p3, &rayOrigin, &rayDirection, &u, &v, &d); 
    isHit2 = FALSE; 

    if(!isHit1) 
    { 
     p1 = vertices[0].position; 
     p2 = vertices[1].position; 
     p3 = vertices[2].position; 
     isHit2 = D3DXIntersectTri(&p1, &p2, &p3, &rayOrigin, &rayDirection, &u, &v, &d); 
    } 

    if(isHit1) 
    { 
     coord.x = 1 * ((1-u-v)*p3.x + u*p3.y + v*p3.z); 
     coord.y = 0.2f; 
     coord.z = -1 * ((1-u-v)*p1.x + u*p1.y + v*p1.z); 
     D3DXVec3TransformCoord(&coord, &coord, &matInverse); 
    } 

    if(isHit2) 
    { 
     coord.x = -1 * ((1-u-v)*p3.x + u*p3.y + v*p3.z); 
     coord.y = 0.2f; 
     coord.z = 1 * ((1-u-v)*p1.x + u*p1.y + v*p1.z); 
     D3DXVec3TransformCoord(&coord, &coord, &matWorld); 
    } 
    return isHit1 || isHit2; 
} 

回答

1

重心座標不像您使用它們那樣工作。 u和v定義源矢量的權重。所以,如果你想計算命中點,你將不得不計算

coord = u * p1 + v * p2 + (1 - u - v) * p3 

另外,您可以使用d線參數:應該導致相同

coord = rayOrigin + d * rDirection 

兩種方式協調。