opengl - 在opengl中围绕固定点旋转对象

Question

我对这个 openGL 代码有疑问：

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix(); // put current matrix on stack

//glTranslatef(0.0f, 0.0f, 0.0f);   
//glTranslatef(-4*1.5, 0.0, 4*1.5);

glRotatef(rotationAngle, 0.0f, 1.0f, 0.0f); // rotate the robot on its y-axis
glTranslatef(xpos, ypos, zpos);
DrawRobot(xpos, ypos, zpos); // draw the robot
glPopMatrix();

我应该怎么做才能让我的机器人绕着它当前所在的点而不是原点转？我认为问题在于这个片段。

Answer 1

沿 z 轴围绕其中心旋转对象的示例：

glPushMatrix();

glTranslatef(250,250,0.0); // 3. Translate to the object's position.

glRotatef(angle,0.0,0.0,1.0); // 2. Rotate the object.

glTranslatef(-250,-250,0.0); // 1. Translate to the origin.

// Draw the object
glPopMatrix();

Answer 2

Simply do the rotation after the translation. The order matters.

glTranslatef(xpos, ypos, zpos);
glRotatef(rotationAngle, 0.0f, 1.0f, 0.0f);

Answer 3

翻译后尝试旋转：

    glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix(); // put current matrix on stack

//glTranslatef(0.0f, 0.0f, 0.0f);   
//glTranslatef(-4*1.5, 0.0, 4*1.5);

glTranslatef(xpos, ypos, zpos);
glRotatef(rotationAngle, 0.0f, 1.0f, 0.0f); // rotate the robot on its y-axis
DrawRobot(xpos, ypos, zpos); // draw the robot
glPopMatrix();

Answer 4

Use this

house();

glTranslatef(x, y, 0.0); // 3. Translate back to original
glRotatef(theta, 0.0, 0.0, 1.0); // 2. Rotate the object around angle
glTranslatef(-m, -n, 0.0); // 1. Move to origin

house();

where m and n are the point on the object around which you want to rotate and x and y are the points around which you want to rotate.