OpenGL，如何相互独立地旋转对象？

Question

到目前为止我的代码

void display ( void )
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity();
gluLookAt(  camera[0][0],       camera[0][1],       camera[0][2],
            camera[1][0],       camera[1][1],       camera[1][2],
            camera[2][0],       camera[2][1],       camera[2][2]            );          //Set the point looking at


glRotatef(cubeRot[0], 1.0f, 0.0f, 0.0f);    //rotate on x axis
glRotatef(cubeRot[1], 0.0f, 1.0f, 0.0f);    //rotate on y axis
glRotatef(cubeRot[2], 0.0f, 0.0f, 1.0f);    //rotate on z axis

switch ( Rendermode ) { //different render mode

    case 'f':
            //Draw object I want to rotate
    break;

    case 'v':
            //Draw object I want to rotate          
    break;

    case 'e':
            //Draw object I want to rotate
    break;

glLoadIdentity();

}

//Draw object I DO NOT want to rotate

glutSwapBuffers ( ); // Swap The Buffers To Not Be Left With A Clear Screen
}

但是，目前我的所有对象都同时旋转，我怎样才能旋转我注意到要旋转的对象，而让我注意到不想旋转的对象保持静止？

Answer 1

使用 glPush/PopMatrix() 封装线性变换并绘制对象。这些函数保存/恢复矩阵的当前状态，因此它们不会影响其他绘图。

glPushMatrix();
glRotatef(...); 
// glTranslatef(...), 
//glScalef(...);
drawObject1();
glPopMatrix();

glPushMatrix();
glRotatef(...); 
// glTranslatef(...), 
//glScalef(...);
drawObject2();
glPopMatrix();

Answer 2

正如@karlphillip 所说，您需要将旋转放入glPush/glPop 矩阵封装中。我认为这段代码应该可以工作：

void display ( void )
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity();
gluLookAt(  camera[0][0],       camera[0][1],       camera[0][2],
            camera[1][0],       camera[1][1],       camera[1][2],
            camera[2][0],       camera[2][1],       camera[2][2]            );          //Set the point looking at

glPushMatrix();  //-------------------- Encapsulate Rotation ----------------
glRotatef(cubeRot[0], 1.0f, 0.0f, 0.0f);    //rotate on x axis
glRotatef(cubeRot[1], 0.0f, 1.0f, 0.0f);    //rotate on y axis
glRotatef(cubeRot[2], 0.0f, 0.0f, 1.0f);    //rotate on z axis

switch ( Rendermode ) { //different render mode

    case 'f':
            //Draw object I want to rotate
    break;

    case 'v':
            //Draw object I want to rotate          
    break;

    case 'e':
            //Draw object I want to rotate
    break;   
}
glPopMatrix(); //------------------- Encapsulate Rotation Ends -------

//Draw object I DO NOT want to rotate

glutSwapBuffers ( ); // Swap The Buffers To Not Be Left With A Clear Screen
}