[英]How to rotate an object around world axis and not local axis in Opengl?
描述:在我的程序中,我確實有一個對象,單擊它時將繪制 3 個旋轉軸。 通過單擊其中一個軸並四處移動鼠標,可以旋轉對象。
問題:對象總是圍繞本地而不是世界軸旋轉,這會導致不良行為。 為了解決這個問題,我嘗試了這個,但是它也不起作用。
代碼:當我加載對象時,我旋轉它使其面向相機。
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));
然后在鼠標移動的事件處理程序中,如果鼠標移動,我將執行進一步的旋轉
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;
}
主循環
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();
}
頂點着色器
#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));
}
你有你的模型視圖矩陣(實際上,它在你的着色器中),但你可以在你的 CPU 中完全相同地計算它。 您只需要將旋轉矩陣的反轉與模型矩陣相乘即可獲得對象空間中的旋轉,然后將其乘以/應用到您的對象。
如果我正確理解您的代碼,您或多或少會這樣做:
World = View * Model * RotationMatrix * Object
然后, RotationMatrix
應用於對象。 如果我了解您的需求,您希望:
World = View * WorldRotationMatrix * Model * Object
然后你只需要求解矩陣方程,使得Model * RotationMatrix2 = WorldRotationMatrix * Model
。
因此,如果A * B = T
,則A-1*A * B = A-1*T => B = A-1 * T
RotationMatrix2 = Model-1 * WorldRotationMatrix * Model
在我上面的符號中, -1
代表矩陣的求逆。
請看這里
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