如何在 Opengl 中围绕世界轴而不是局部轴旋转对象？

Question

说明： 在我的程序中，我确实有一个对象，单击它时将绘制 3 个旋转轴。通过单击其中一个轴并移动鼠标，可以旋转对象。

问题： 对象总是围绕局部而不是世界轴旋转，这会导致不良行为。 为了解决这个问题，我尝试了this，但它也不起作用。

代码： 当我加载对象时，我会旋转它，使其面向相机。

    m_phantomRotationMatrix = glm::rotate(m_phantomRotationMatrix, -90 * glm::pi<float>() / 180.0f, glm::vec3(1.0f, 0.0f, 0.0f));
    m_phantomRotationMatrix = glm::rotate(m_phantomRotationMatrix, 90 * glm::pi<float>() / 180.0f, glm::vec3(0.0f, 0.0f, 1.0f));

然后在鼠标移动的事件处理程序中，如果鼠标移动，我将执行进一步的旋转

        case 5: // X rotation axis
        {
            GLfloat xCurrentPosition = wxGetMousePosition().x;
            GLfloat yCurrentPosition = wxGetMousePosition().y;

            m_phantomRotationMatrix = glm::rotate(m_phantomRotationMatrix, (xCurrentPosition - m_xLastPosition) * glm::pi<float>() / 180.0f, glm::vec3(1.0f, 0.0f, 0.0f));

            m_xLastPosition = xCurrentPosition;
            m_yLastPosition = yCurrentPosition;
            break;
        }
        case 6: // Y rotation axis
        {
            GLfloat xCurrentPosition = wxGetMousePosition().x;
            GLfloat yCurrentPosition = wxGetMousePosition().y;

            m_phantomRotationMatrix = glm::rotate(m_phantomRotationMatrix, (yCurrentPosition - m_yLastPosition) * glm::pi<float>() / 180.0f, glm::vec3(0.0f, 1.0f, 0.0f));

            m_xLastPosition = xCurrentPosition;
            m_yLastPosition = yCurrentPosition;
            break;
        }
        case 7: // Z rotation axis
        {
            GLfloat xCurrentPosition = wxGetMousePosition().x;
            GLfloat yCurrentPosition = wxGetMousePosition().y;

            m_phantomRotationMatrix = glm::rotate(m_phantomRotationMatrix, (xCurrentPosition - m_xLastPosition) * glm::pi<float>() / 180.0f, glm::vec3(0.0f, 0.0f, 1.0f));

            m_xLastPosition = xCurrentPosition;
            m_yLastPosition = yCurrentPosition;
            break;
        }

主循环

void MyGLCanvas::draw(wxDC& dc)
{
    wxGLCanvas::SetCurrent(*m_glContext);
    glEnable(GL_MULTISAMPLE);
    glViewport(0, 0, m_windowWidth, m_windowHeight);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_STENCIL_TEST);
    glClearDepth(1.0f);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glDepthFunc(GL_LEQUAL);

    m_rotationAngleAroundPhantom++;
    glm::mat4 phantomModel, view, projection;
    phantomModel = glm::translate(phantomModel, m_phantomPosition);
    view = m_fpsCamera->getViewMatrix();
    projection = m_fpsCamera->getProjectionMatrix(m_windowWidth, m_windowHeight);
    m_color = glm::vec4(0.310f, 0.747f, 0.185f, 1.0f);
    glm::vec3 lightPos = glm::vec3(0.0f, 1.0f, 0.0f);
    glm::vec3 lightColor = glm::vec3(1.0f, 1.0f, 1.0f);

    ShaderProgram shaderProgram;
    shaderProgram.loadShaders("Shaders/phantom.vert", "Shaders/phantom.frag");

    glClearStencil(0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    shaderProgram.use();
    shaderProgram.setUniform("phantomRotationMatrix", m_phantomRotationMatrix);
    shaderProgram.setUniform("model", phantomModel);
    shaderProgram.setUniform("view", view);
    shaderProgram.setUniform("projection", projection);
    shaderProgram.setUniform("color", m_color);
    shaderProgram.setUniform("lightColor", lightColor);
    shaderProgram.setUniform("lightPos", m_fpsCamera->getPosition());
    shaderProgram.setUniform("cameraPos", m_fpsCamera->getPosition());

    glStencilMask(0xFF); // Write to stencil buffer
    glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
    glStencilFunc(GL_ALWAYS, 0, 0xFF);  // Set any stencil to 0

    glStencilFunc(GL_ALWAYS, 1, 0xFF); // Set any stencil to object ID
    m_pantomMesh->draw();
    glStencilFunc(GL_ALWAYS, 0, 0xFF);  // Set any stencil to 0
    shaderProgram.deleteProgram();

    if (phantomIsSelected && leftMouseClicked)
    {
        drawMovementAxes(phantomModel, view, projection);
    }

    if (phantomIsSelected && rightMouseClicked)
    {
        drawRotationAxes(phantomModel, view, projection);
    }

    glFlush();
    wxGLCanvas::SwapBuffers();
}

顶点着色器

#version 330 core

layout (location = 0) in vec3 pos;
layout (location = 1) in vec3 normal;
out vec4 vert_color;
out vec3 Normal;
out vec3 FragPos;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
uniform mat4 phantomRotationMatrix;
uniform vec4 color;

void main()
{
    vert_color = color;
    gl_Position = projection * view * model * phantomRotationMatrix * vec4(pos.x, pos.y, pos.z, 1.0);
    FragPos = vec3(model * phantomRotationMatrix * vec4(pos, 1.0));
    Normal = vec3(transpose(inverse(phantomRotationMatrix)) * vec4(normal, 0.0));
}

Answer 1

您有模型视图矩阵（实际上，它在您的着色器中），但您可以在 CPU 中完全一样地计算它。您只需要将旋转矩阵的倒数与模型矩阵相乘，即可获得对象空间中的旋转，然后将其相乘/应用到您的对象。

如果我正确理解你的代码，你或多或少会这样做：

   World = View * Model * RotationMatrix * Object

然后，RotationMatrix 应用于 Object。 如果我了解您的需求，您希望：

   World = View * WorldRotationMatrix * Model * Object

那么你只需要解矩阵方程，使Model * RotationMatrix2 = WorldRotationMatrix * Model。

因此，如果A * B = T，A-1*A * B = A-1*T => B = A-1 * T

RotationMatrix2 = Model-1 * WorldRotationMatrix * Model

在我上面的符号中，-1 代表矩阵的反转。

请看here