通过 DirectX12 工具包进行挑选

Question

我在尝试使 3d 对象可通过鼠标单击时遇到问题。 对于交叉点检查，我使用光线投射。 我找到的代码，为我的解决方案移植：

准确采摘

bool RaySphereIntersect(Vector3, Vector3, float);

bool TestIntersection(Matrix projectionMatrix, Matrix viewMatrix, Matrix worldMatrix, Vector3 origin, float radius, int m_screenWidth, int m_screenHeight, int mouseX, int mouseY)
{
float pointX, pointY;
Matrix inverseViewMatrix, translateMatrix, inverseWorldMatrix;
Vector3 direction, rayOrigin, rayDirection;

bool intersect, result;

// Move the mouse cursor coordinates into the -1 to +1 range.
pointX = ((2.0f * (float)mouseX) / (float)m_screenWidth) - 1.0f;
pointY = (((2.0f * (float)mouseY) / (float)m_screenHeight) - 1.0f) * -1.0f;

// Adjust the points using the projection matrix to account for the aspect ratio of the viewport.
pointX = pointX / projectionMatrix._11;
pointY = pointY / projectionMatrix._22;

// Get the inverse of the view matrix.
inverseViewMatrix=XMMatrixInverse(NULL, viewMatrix);

// Calculate the direction of the picking ray in view space.
direction.x = (pointX * inverseViewMatrix._11) + (pointY * inverseViewMatrix._21) + inverseViewMatrix._31;
direction.y = (pointX * inverseViewMatrix._12) + (pointY * inverseViewMatrix._22) + inverseViewMatrix._32;
direction.z = (pointX * inverseViewMatrix._13) + (pointY * inverseViewMatrix._23) + inverseViewMatrix._33;

// Get the origin of the picking ray which is the position of the camera.
// Get the world matrix and translate to the location of the sphere.
// Now get the inverse of the translated world matrix.
inverseWorldMatrix= XMMatrixInverse(NULL, worldMatrix);

// Now transform the ray origin and the ray direction from view space to world space.
rayOrigin=XMVector3TransformCoord(origin, inverseWorldMatrix);
rayDirection=XMVector3TransformNormal(direction, inverseWorldMatrix);

// Normalize the ray direction.
rayDirection=XMVector3Normalize(rayDirection);



// Now perform the ray-sphere intersection test.
intersect = RaySphereIntersect(rayOrigin, rayDirection, radius);

if (intersect == true)
 return true;
else
 return false;

}



 bool RaySphereIntersect(Vector3 rayOrigin, Vector3 rayDirection, float radius)
 {
 float a, b, c, discriminant;
 // Calculate the a, b, and c coefficients.
 a = (rayDirection.x * rayDirection.x) + (rayDirection.y * rayDirection.y) + (rayDirection.z * rayDirection.z);
 b = ((rayDirection.x * rayOrigin.x) + (rayDirection.y * rayOrigin.y) + (rayDirection.z * rayOrigin.z)) * 2.0f;
 c = ((rayOrigin.x * rayOrigin.x) + (rayOrigin.y * rayOrigin.y) + (rayOrigin.z * rayOrigin.z)) - (radius * radius);

// Find the discriminant.
discriminant = (b * b) - (4 * a * c);

// if discriminant is negative the picking ray missed the sphere, otherwise it intersected the sphere.
 if (discriminant < 0.0f)
 return false;
 else
 return true;

 }

如何创建球体

D3DSphere(float x, float y, float z, float radius, float r, float g, float b, float a)  
{
this->x = x;
this->y = y;
this->z = z;

this->radius = radius;

this->shape = GeometricPrimitive::CreateSphere(radius*2.0f);

this->world = Matrix::Identity;
this->world = XMMatrixMultiply(this->world, Matrix::CreateTranslation(x, y, z));
this->index = vsphere;

d3dsphere[vsphere] = this;
vsphere++;
}

我如何调用 raycaster

void Game::LButtonUp(int x, int y)
{
Vector3 eye(camx, camy, camz);
Vector3 at(Vector3::Zero);
m_view = Matrix::CreateLookAt(eye, at, Vector3::UnitY);
for (int i = 0; i < vsphere; i++)
{
if (TestIntersection(m_projection, m_view, d3dsphere[i]->world, eye, d3dsphere[i]->radius, 800, 600, x, y))
{
MessageBoxW(NULL, L"LOL", L"It works", MB_OK);

break;
}
}

}

单击没有任何反应，但是如果我垂直于 XOY 旋转相机，有时在球体附近单击，会出现消息框。

---

更新

MessageBox 在摄像机角度上独立出现，并且似乎正确地检测到交叉点，但相对于 window 中心是镜像的。 例如，如果球体位于(0, window.bottom-20)点，那么如果单击(0, 20)点，我将获得 MessageBox。

如果拾取射线的方向计算错误，如果它是为左手系统编写的，而我使用右手系统怎么办？

Answer 1

可能是因为右手系统，DirectX Tool Kit 中默认使用的系统 下一节来自 caster

pointX = ((2.0f * (float)mouseX) / (float)m_screenWidth) - 1.0f;
pointY = (((2.0f * (float)mouseY) / (float)m_screenHeight) - 1.0f) * -1.0f; 

应改为

pointX = (((2.0f * (float)mouseX) / (float)m_screenWidth) - 1.0f) * -1.0f;
pointY = (((2.0f * (float)mouseY) / (float)m_screenHeight) - 1.0f); 

重要的

由于深度独立，该代码也将出错，即您可能位于您单击的球体后面的 select 球体。 为了解决我更改了代码：

float distance3(float x1, float y1, float z1, float x2, float y2, float z2)
{
float dx=x1-x2;
float dy=y1-y2;
float dz=z1-z2;
return sqrt(dx*dx+dy*dy+dz*dz);
}

void Game::LButtonUp(int x, int y)
{
Vector3 eye(camx, camy, camz);
Vector3 at(Vector3::Zero);
m_view = Matrix::CreateLookAt(eye, at, Vector3::UnitY);
int last_index=-1;
float last_distance=99999.0f;//set the obviously highest value, may happen in your scene

for (int i = 0; i < vsphere; i++)
{
if (TestIntersection(m_projection, m_view, d3dsphere[i]->world, eye, d3dsphere[i]->radius, 800, 600, x, y))
{
float distance=distance3(camx,camy,camz, d3dsphere[i]->x, d3dsphere[i]->y, d3dsphere[i]->z);
if(distance<last_distance)
{
last_distance=distance;
last_index=i;
}
}
}

d3dsphere[last_index];//picked sphere 
}