OpenGL 奇怪的鼠标旋转结果

Question

So I'm working on a 3d painting application. I managed to make a basic renderer and model loader.

I created a camera system where I can use it to navigate around the scene(mouse/keyboard) but that's not what I want, so I made that camera static and now I'm trying to rotate/pan/zoom the model itself . I managed to implement panning and zooming . for panning i change the x/y position according to the mouse and for zooming I add or substract from the z-axis according to the mouse scroll.

But now I want to be able to rotate the 3d model with the mouse . Example: When i hold right mouse button and move the mouse up the model should rotate on it's x-axis(pitch) and if i move the mouse to the left/right it should rotate on y-axis(yaw) . And I just couldn't do it.

The code bellow I get xpos/ypos of the cursor on the screen, calculate the offset and " trying to rotate the cube ". The only problem is that i can't rotate the cuber normally if i move the mouse up the model rotate on the x-axis and y-axis with a little tilt and vice-versa.

This is the code in my rendering loop:

    shader.use();
    glm::mat4 projection = glm::perspective(glm::radians(45.0f), 
    (float)SCR_WIDTH/(float)SCR_HEIGHT, 0.01f, 100.0f);
    shader.setMat4f("projection", projection);

    glm::mat4 view = camera.getViewMatrix();
    shader.setMat4f("view", view);

    glm::mat4 modelm = glm::mat4(1.0f);
    modelm = glm::translate(modelm, object_translation);
    // Should rotate cube according to mouse movement
    //modelm = glm::rotate(modelm, glm::radians(angle), glm::vec3(0.0f));
    shader.setMat4f("model", modelm);

    renderer.draw(model, shader);

This is the call where i handle the mouse movement callback:

void mouseCallback(GLFWwindow* window, double xpos, double ypos)
{
if (is_rotating)
{
    if (is_first_mouse)
    {
        lastX = xpos;
        lastY = ypos;
        is_first_mouse = false;
    }

    // xpos and ypos are the cursor coords i get those with the 
    mouse_callback
    double xoffset = xpos - lastX;
    double yoffset = lastY - ypos;

    lastX = xpos;
    lastY = ypos;

    object_rotation.y += xoffset; // If i use yoffset the rotation flips
    object_rotation.x += yoffset;

    rotation_angle += (xoffset + yoffset) * 0.25f;
}
}

Mouse panning works fine too can't say the same for the rotation.

Answer 1

I fixed it. After some research and asking i was told that u can only do one rotation at a time and i was trying to do both x/y-axis in the same time . Once i seperate the two rotations. object will now rotate on x-axis first then y-axis the problem was solved.

The code should be like this:

    shader.use();
    glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float)SCR_WIDTH/(float)SCR_HEIGHT, 0.01f, 100.0f);
    shader.setMat4f("projection", projection);

    glm::mat4 view = camera.getViewMatrix();
    shader.setMat4f("view", view);

    glm::mat4 modelm = glm::mat4(1.0f);
    modelm = glm::scale(modelm, glm::vec3(1.0f));
    modelm = glm::translate(modelm, glm::vec3(0.0f, 0.0f, -5.0f));
    // Handle x-axis rotation
    modelm = glm::rotate(modelm, glm::radians(object_orientation_angle_x), glm::vec3(object_rotation_x, 0.0f, 0.0f));
    // Handle y-axis rotation
    modelm = glm::rotate(modelm, glm::radians(object_orientation_angle_y), glm::vec3(0.0f, object_rotation_y, 0.0f));
    shader.setMat4f("model", modelm);

    renderer.draw(model, shader);

Answer 2

You are storing your rotation as euler angle inside object_rotation.

I advised you to use:

glm::mat4 rotation = glm::eulerAngleYX(object_rotation.y, object_rotation.x); // pitch then yaw

or

glm::mat4 rotation = glm::eulerAngleXY(object_rotation.x, object_rotation.y); // yaw then roll

In your case both should do the job, I advised you in the future to store thoose informations inside your camera (eye, up, center) instead of your object, everything become more simpler.