How to draw cylinder in y or x axis in opengl

问题:

I just want to draw a cylinder in opengl. I found lots of samples but all of them draws cylinders in z axis. I want them be in x or y axis. How can i do this. The code below is the code draw the cylinder in z direction and i dont want it

  GLUquadricObj *quadratic;
  quadratic = gluNewQuadric();
  gluCylinder(quadratic,0.1f,0.1f,3.0f,32,32);

回答1:

You can use glRotate(angle, x, y, z) to rotate your coordinate system:

GLUquadricObj *quadratic;
quadratic = gluNewQuadric();
glRotatef(90.0f, 0.0f, 1.0f, 0.0f);
gluCylinder(quadratic,0.1f,0.1f,3.0f,32,32);

http://www.opengl.org/sdk/docs/man/xhtml/glRotate.xml

回答2:

On every render use glPushMatrix glRotatef draw the cylinder and finish your drawing with glPopMatrix.

Ex.: glRotatef(yRotationAngle, 0.0f, 1.0f, 0.0f); // Rotate your object around the y axis on yRotationAngle radians

Ex.: OnRender() function example

void OnRender() {
  glClearColor(1.0f, 0.0f, 0.0f, 1.0f); // Clear the background
  glClear(GL_COLOR_BUFFER_BIT); //Clear the colour buffer
  glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations

  glRotatef(yRotationAngle, 0.0f, 1.0f, 0.0f); // Rotate our object around the y axis on yRotationAngle radians

  // here *render* your cylinder (create and delete it in the other place. Not while rendering)
  gluCylinder(quadratic,0.1f,0.1f,3.0f,32,32);

  glFlush(); // Flush the OpenGL buffers to the window  
}