glm库-改变mvp矩阵-控制视角或模型

投影矩阵

    QMatrix4x4 m_projection;
   

投影矩阵计算

【相机的视场角fov,最近距离，zNear，最远距离zFar,宽高比aspect】

    qreal aspect = qreal((mWidth)) / qreal(mHeight ? mHeight : 1);
    // Set near plane to 3.0, far plane to 7.0, field of view 45 degrees
    const qreal zNear = 0.2, zFar = 10000.0, fov = 75.0;

    m_projection.setToIdentity();
    m_projection.perspective(fov, aspect, zNear, zFar);

这个体型区域内的额 物体会被投影。

view 矩阵

描述相机（眼睛）是怎么观察 物体 的。

    void updateCameraVectors()
    {
        glm::vec3 front;
        front.x = -sin(glm::radians(Yaw)); //偏航角为正数，偏向x负半轴
        front.y = sin(glm::radians(Pitch));
        front.z = -cos(glm::radians(Pitch)) * cos(glm::radians(Yaw));
        Front = glm::normalize(front);
        Right = glm::normalize(glm::cross(Front, WorldUp));
        Up = glm::normalize(glm::cross(Right, Front));
        DEBUG_LOG("cam position : %f %f %f\n",Position.x,Position.y,Position.z);
        DEBUG_LOG("cam rot : yaw %f pitch %f \n",Yaw,Pitch);
    }
    glm::mat4 GetViewMatrix() {
        return glm::lookAt(Position, Position + Front, Up);
    }

glm::mat4 view = virtualCamera::GetViewMatrix();

model 矩阵控制模型旋转

 QMatrix4x4 model;
    model.rotate(m_xrot, 1.0f, 0.0f, 0.0f);
    model.rotate(m_yrot, 0.0f, 1.0f, 0.0f);
    model.rotate(m_zrot, 0.0f, 0.0f, 1.0f);

MVP model view project 矩阵（其实是 project * view * model *obj)

将obj 坐标 渲染到屏幕上面的（u,v）点

（u,v) = projectMatrix * view * model * obj

QMatrix4x4 matrix(
                view[0][0],view[1][0],view[2][0],view[3][0],
                view[0][1],view[1][1],view[2][1],view[3][1],
                view[0][2],view[1][2],view[2][2],view[3][2],
                view[0][3],view[1][3],view[2][3],view[3][3]
            );
m_program->setUniformValue("mvpMatrix", m_projection * matrix * model);

参考文档

https://blog.csdn.net/zhangpengzp/article/details/88749779

https://www.itranslater.com/qa/details/2582874717636002816

http://www.dovov.com/glm-lookat.html