尝试在 OpenGL 3 中进行鼠标拾取时获取不正确的向量

Question

我正在尝试获取屏幕上光标所在位置的方向矢量，但它给了我很大的值而不是实际值。在进行鼠标拾取时，我的世界坐标得到的数字非常小，例如

Mouse is pointing at World X: 4.03225e-05 Y: -0.00048387 Z: -1

我是不是做错了什么，我已经从改编了这段代码。我正在使用 glm::intersectLineTriangle() 来测试直线是否指向有问题的三角形世界坐标。

相关代码如下：

double mouse_x, mouse_y;
glfwGetCursorPos(GL::g_window, &mouse_x, &mouse_y);

int width, height;
glfwGetFramebufferSize(GL::g_window, &width, &height);

// these positions must be in range [-1, 1] (!!!), not [0, width] and [0, height]
float mouseX = (float)mouse_x / ((float)width  * 0.5f) - 1.0f;
float mouseY = (float)mouse_y / ((float)height * 0.5f) - 1.0f;

glm::mat4 invVP = glm::inverse(projection * view);
glm::vec4 screenPos = glm::vec4(mouseX, -mouseY, 1.0f, 1.0f);
glm::vec4 worldPos = invVP * screenPos;

glm::vec3 mouseClickVec = glm::normalize(glm::vec3(worldPos));

std::cout << "Mouse is pointing at World X: " << mouseClickVec.x <<  " Y: " << mouseClickVec.y << " Z: " << mouseClickVec.z << '\n';

glm::vec3 intersect;

if(glm::intersectLineTriangle(glm::vec3(0.0f, 0.0f, 0.0f), mouseClickVec, m_vertices_world[0], m_vertices_world[0], m_vertices_world[0], intersect))
{
 std::cout << "Intersect at X: " << intersect.x <<  " Y: " << intersect.y << " Z: " << intersect.z << '\n';
 setColor(glm::vec4(0.0f, 0.0f, 1.0f, 1.0f));
}
else
{
    setColor(glm::vec4(1.0f, 0.0f, 0.0f, 1.0f));
}

Answer 1

使用正交（平行）投影时，视点不是(0, 0, 0)，（不在视野space当然也不在世界space）。您必须创建一条从近平面 (-1) 到远平面 (1) 的射线：

glm::vec4 worldPosFar = invVP * glm::vec4(mouseX, -mouseY, 1.0f, 1.0f);
glm::vec3 mouseClickVecFar = glm::normalize(glm::vec3(worldPosFar));

glm::vec4 worldPosNear = invVP * glm::vec4(mouseX, -mouseY, -1.0f, 1.0f);
glm::vec3 mouseClickVecNear = glm::normalize(glm::vec3(worldPosNear));

if (glm::intersectLineTriangle(mouseClickVecNear, mouseClickVecFar,
    m_vertices_world[0], m_vertices_world[0], m_vertices_world[0], intersect))
{
    // [...]
}

尝试在 OpenGL 3 中进行鼠标拾取时获取不正确的向量

Getting incorrect vectors when trying to do mouse picking in OpenGL 3

c++

opengl

glm-math

opengl-3

mouse-picking