从D3DXIntersectTri获取世界坐标 [英] Get world coordinates from D3DXIntersectTri
问题描述
我有一个正方形区域,必须确定鼠标指向的位置。
使用D3DXIntersectTri可以告诉我鼠标是否指向其上,但是我在计算x,y,z时遇到麻烦
I have a square area on which I have to determine where the mouse pointing.
With D3DXIntersectTri I can tell IF the mouse pointing on it, but I have trouble calculating the x,y,z coordinates.
来自顶点缓冲区的图形,并使用vertices数组进行了初始化:
The drawing from vertex buffer, which initialized with the vertices array:
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);
到目前为止,我有此方法,但这不能给我正确的坐标(仅适用于小区域的一部分,靠近两个边缘,内部更不准确):
I have this method so far, this is not giving me the right coordinates (works only on a small part of the area, near two of the edges and more less accurate inside):
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;
}
推荐答案
重心坐标不起作用您使用它们的方式。 u和v定义源向量的权重。因此,如果要计算命中点,则必须计算
Barycentric coordinates don't work the way you used them. u and v define the weight of the source vectors. So if you want to calculate the hit point, you will have to compute
coord = u * p1 + v * p2 + (1 - u - v) * p3
也可以使用d ray参数:
Alternatively you can use the d ray parameter:
coord = rayOrigin + d * rDirection
两种方式都应产生相同的坐标。
Both ways should result in the same coordinate.
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