libigl_Martin/examples/camera/example.cpp

#include <igl/Viewport.h>
#include <igl/report_gl_error.h>
#include <igl/ReAntTweakBar.h>
#include <igl/trackball.h>
#include <igl/two_axis_valuator_fixed_up.h>
#include <igl/PI.h>
#include <igl/EPS.h>
#include <igl/get_seconds.h>
#include <igl/draw_floor.h>

#include <Eigen/Core>
#include <Eigen/Geometry>

#ifdef WIN32
#include <GL/glut.h>
#else
#include <GLUT/glut.h>
#endif

#include <vector>
#include <stack>
#include <iostream>

class Camera
{
  public:
    //  m_zoom   Zoom of camera lens {1}
    //  m_angle  Field of view angle in degrees {45}
    //  m_aspect  Aspect ratio {1}
    //  m_near  near clipping plane {1e-2}
    //  m_far  far clipping plane {100}
    //  m_at_dist  distance of looking at point {1}
    //  m_rotation  Rotation part of rigid transformation of camera {identity}.
    //    Note that this seems to the inverse of what's stored in the old
    //    igl::Camera class.
    //  m_translation  Translation part of rigid transformation of camera
    //    {(0,0,1)}
    double m_zoom, m_angle, m_aspect, m_near, m_far, m_at_dist;
    Eigen::Quaterniond m_rotation;
    Eigen::Vector3d m_translation;
    Camera():
      m_zoom(1),m_angle(45.0),m_aspect(1),m_near(1e-2),m_far(100),m_at_dist(1),
      m_rotation(1,0,0,0),
      m_translation(0,0,1)
    {
    }

    // Return projection matrix that takes relative camera coordinates and
    // transforms it to viewport coordinates
    Eigen::Matrix4d projection() const
    {
      Eigen::Matrix4d P;
      using namespace std;
      using namespace igl;
      // http://stackoverflow.com/a/3738696/148668
      const double yScale = tan(PI*0.5 - 0.5*m_angle*PI/180.);
      // http://stackoverflow.com/a/14975139/148668
      const double xScale = yScale/m_aspect;
      P<< 
        xScale, 0, 0, 0,
        0, yScale, 0, 0,
        0, 0, -(m_far+m_near)/(m_far-m_near), -1,
        0, 0, -2.*m_near*m_far/(m_far-m_near), 0;
      return P.transpose();
    }

    // Return an Affine transformation that takes a world 3d coordinate and
    // transforms it into the relative camera coordinates.
    Eigen::Affine3d affine() const
    {
      using namespace Eigen;
      Affine3d t = Affine3d::Identity();
      t.rotate(m_rotation);
      t.translate(m_translation);
      return t;
    }

    // Returns world coordinates position of center or "eye" of camera.
    Eigen::Vector3d eye() const
    {
      using namespace Eigen;
      return affine() * Vector3d(0,0,0);
    }

    // Returns world coordinate position of a point "eye" is looking at.
    Eigen::Vector3d at() const
    {
      using namespace Eigen;
      return affine() * (Vector3d(0,0,-1)*m_at_dist);
    }

    // Returns world coordinate unit vector of "up" vector
    Eigen::Vector3d up() const
    {
      using namespace Eigen;
      Affine3d t = Affine3d::Identity();
      t.rotate(m_rotation);
      return t * Vector3d(0,1,0);
    }

    // Move dv in the relative coordinate frame of the camera (move the FPS)
    //
    // Inputs:
    //   dv  (x,y,z) displacement vector
    //
    void dolly(const Eigen::Vector3d & dv)
    {
      m_translation += dv;
    }

    // "Scale zoom": Move `eye`, but leave `at`
    //
    // Input:
    //   s  amount to scale distance to at
    void push_away(const double s)
    {
      using namespace Eigen;
#ifndef NDEBUG
      Vector3d old_at = camera.at();
#endif
      const double old_at_dist = m_at_dist;
      m_at_dist = old_at_dist * s;
      dolly(Vector3d(0,0,1)*(m_at_dist - old_at_dist));
      assert((old_at-camera.at()).squaredNorm() < DOUBLE_EPS);
    }

    // Aka "Hitchcock", "Vertigo", "Spielberg" or "Trombone" zoom:
    // simultaneously dolly while changing angle so that `at` not only stays
    // put in relative coordinates but also projected coordinates. That is
    //
    // Inputs:
    //   da  change in angle in degrees
    void dolly_zoom(const double da)
    {
      using namespace std;
      using namespace Eigen;
#ifndef NDEBUG
      Vector3d old_at = camera.at();
#endif
      const double old_angle = m_angle;
      m_angle += da;
      m_angle = min(89.,max(5.,m_angle));
      const double s = 
        (2.*tan(old_angle/2./180.*M_PI)) /
        (2.*tan(m_angle/2./180.*M_PI)) ;
      const double old_at_dist = m_at_dist;
      m_at_dist = old_at_dist * s;
      dolly(Vector3d(0,0,1)*(m_at_dist - old_at_dist));
      assert((old_at-camera.at()).squaredNorm() < DOUBLE_EPS);
    }

    // Return top right corner of unit plane in relative coordinates, that is
    // (w/2,h/2,1)
    Eigen::Vector3d unit_plane() const
    {
      using namespace igl;
      // Distance of center pixel to eye
      const double d = 1.0;
      const double a = m_aspect;
      const double theta = m_angle*PI/180.;
      const double w =
        2.*sqrt(-d*d/(a*a*pow(tan(0.5*theta),2.)-1.))*a*tan(0.5*theta);
      const double h = w/a;
      return Eigen::Vector3d(w*0.5,h*0.5,-d);
    }

    // Rotate and translate so that camera is situated at "eye" looking at "at"
    // with "up" pointing up.
    //
    // Inputs:
    //   eye  (x,y,z) coordinates of eye position
    //   at   (x,y,z) coordinates of at position
    //   up   (x,y,z) coordinates of up vector
    void look_at(
      const Eigen::Vector3d & eye,
      const Eigen::Vector3d & at,
      const Eigen::Vector3d & up)
    {
      using namespace Eigen;
      using namespace std;
      using namespace igl;
      // http://www.opengl.org/sdk/docs/man2/xhtml/gluLookAt.xml
      // Normalize vector from at to eye
      Vector3d F = eye-at;
      m_at_dist = F.norm();
      F.normalize();
      // Project up onto plane orthogonal to F and normalize
      const Vector3d proj_up = (up-(up.dot(F))*F).normalized();
      Quaterniond a,b;
      a.setFromTwoVectors(Vector3d(0,0,-1),-F);
      b.setFromTwoVectors(a*Vector3d(0,1,0),proj_up);
      m_rotation = a*b;
      m_translation = m_rotation.conjugate() * eye;
      assert(           (eye-this->eye()).squaredNorm() < DOUBLE_EPS);
      assert((F-(this->eye()-this->at()).normalized()).squaredNorm() < 
        DOUBLE_EPS);
      assert(           (at-this->at()).squaredNorm() < DOUBLE_EPS);
      assert(        (proj_up-this->up()).squaredNorm() < DOUBLE_EPS);
    }

};

enum RotationType
{
  ROTATION_TYPE_IGL_TRACKBALL = 0,
  ROTATION_TYPE_TWO_AXIS_VALUATOR_FIXED_UP = 1,
  NUM_ROTATION_TYPES = 2,
} rotation_type = ROTATION_TYPE_TWO_AXIS_VALUATOR_FIXED_UP;

enum CenterType
{
  CENTER_TYPE_ORBIT = 0,
  CENTER_TYPE_FPS  = 1,
  NUM_CENTER_TYPES = 2,
} center_type = CENTER_TYPE_ORBIT;

int width,height;
#define REBAR_NAME "temp.rbr"
igl::ReTwBar rebar;
struct State
{
  int viewing_camera;
  std::vector<Camera> cameras;
  std::vector<GLuint> tex_ids;
  std::vector<GLuint> fbo_ids;
  std::vector<GLuint> dfbo_ids;
  State():viewing_camera(0),cameras(4),
    tex_ids(cameras.size()),
    fbo_ids(cameras.size()),
    dfbo_ids(cameras.size())
    {}
} s;
const Eigen::Vector4d back(1,1,1,1);
std::stack<State> undo_stack;
bool is_rotating = false;
Camera down_camera;
int down_x,down_y;
std::stack<State> redo_stack;

void push_undo()
{
  undo_stack.push(s);
  // Clear
  redo_stack = std::stack<State>();
}

void undo()
{
  if(!undo_stack.empty())
  {
    redo_stack.push(s);
    s = undo_stack.top();
    undo_stack.pop();
  }
}

void redo()
{
  if(!redo_stack.empty())
  {
    undo_stack.push(s);
    s = redo_stack.top();
    redo_stack.pop();
  }
}

void print(const Camera & camera)
{
  using namespace std;
  cout<<
    "rotation:    "<<camera.m_rotation.coeffs().transpose()<<endl<<
    "translation: "<<camera.m_translation.transpose()<<endl<<
    "eye:         "<<camera.eye().transpose()<<endl<<
    "at:          "<<camera.at().transpose()<<endl<<
    "up:          "<<camera.up().transpose()<<endl<<
    endl;
}

void init_cameras()
{
  using namespace Eigen;
  using namespace std;
  s.cameras[0].look_at(
    Vector3d(0,0,1),
    Vector3d(0,0,0),
    Vector3d(0,1,0));
  s.cameras[1].look_at(
    Vector3d(0,0,-1),
    Vector3d(0,0,0),
    Vector3d(0,1,0));
  s.cameras[2].look_at(
    Vector3d(-2,0,0),
    Vector3d(0,0,0),
    Vector3d(0,1,0));
  s.cameras[3].look_at(
    Vector3d(3,0,0),
    Vector3d(0,0,0),
    Vector3d(0,1,0));
}

bool init_render_to_texture(
  const int width, 
  const int height, 
  GLuint & tex_id, 
  GLuint & fbo_id, 
  GLuint & dfbo_id)
{
  using namespace igl;
  using namespace std;
  // Set up a "render-to-texture" frame buffer and texture combo
  glDeleteTextures(1,&tex_id);
  glDeleteFramebuffersEXT(1,&fbo_id);
  glDeleteFramebuffersEXT(1,&dfbo_id);
  // http://www.opengl.org/wiki/Framebuffer_Object_Examples#Quick_example.2C_render_to_texture_.282D.29
  glGenTextures(1, &tex_id);
  glBindTexture(GL_TEXTURE_2D, tex_id);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  //NULL means reserve texture memory, but texels are undefined
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
  glBindTexture(GL_TEXTURE_2D, 0);
  //-------------------------
  glGenFramebuffersEXT(1, &fbo_id);
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo_id);
  //Attach 2D texture to this FBO
  glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex_id, 0);
  glGenRenderbuffersEXT(1, &dfbo_id);
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, dfbo_id);
  glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, width, height);
  //-------------------------
  //Attach depth buffer to FBO
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, dfbo_id);
  //-------------------------
  //Does the GPU support current FBO configuration?
  GLenum status;
  status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
  switch(status)
  {
    case GL_FRAMEBUFFER_COMPLETE_EXT:
      break;
    default:
      return false;
  }
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, 0);
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
  return true;
}

void reshape(int width, int height)
{
  ::width = width;
  ::height = height;
  glViewport(0,0,width,height);
  // Send the new window size to AntTweakBar
  TwWindowSize(width, height);
}


void draw_scene(const Camera & v_camera,
  const bool render_to_texture,
  const GLuint & v_tex_id, 
  const GLuint & v_fbo_id, 
  const GLuint & v_dfbo_id)
{
  using namespace igl;
  using namespace std;
  using namespace Eigen;

  if(render_to_texture)
  {
    // render to framebuffer
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, v_fbo_id);
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, v_dfbo_id);
    glClearColor(back(0),back(1),back(2),1);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  }

  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
  glLoadIdentity();
  //gluPerspective(v_camera.m_angle,v_camera.m_aspect,v_camera.m_near,v_camera.m_far);
  glMultMatrixd(v_camera.projection().data());
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  glLoadIdentity();
  gluLookAt(
    v_camera.eye()(0), v_camera.eye()(1), v_camera.eye()(2),
    v_camera.at()(0), v_camera.at()(1), v_camera.at()(2),
    v_camera.up()(0), v_camera.up()(1), v_camera.up()(2));

  for(int c = 0;c<(int)s.cameras.size();c++)
  {
    auto & camera = s.cameras[c];
    if(&v_camera == &camera)
    {
      continue;
    }
    // draw camera
    glPushMatrix();
    glMultMatrixd(camera.affine().matrix().data());
    // eye
    glColor4f(0,0,0,1);
    glPointSize(10.f);
    glBegin(GL_POINTS);
    glVertex3f(0,0,0);
    glEnd();
    // frustrum
    const Vector3d u = camera.unit_plane();
    glBegin(GL_LINES);
    for(int x = -1;x<=1;x+=2)
    {
      for(int y = -1;y<=1;y+=2)
      {
        glVertex3f(0,0,0);
        glVertex3f(x*u(0),y*u(1),u(2));
      }
    }
    glEnd();
    const Vector3d n = u*(camera.m_near-FLOAT_EPS);
    glBegin(GL_QUADS);
      glVertex3f( n(0),-n(1),n(2));
      glVertex3f(-n(0),-n(1),n(2));
      glVertex3f(-n(0), n(1),n(2));
      glVertex3f( n(0), n(1),n(2));
    glEnd();
    for(int pass = 0;pass<2;pass++)
    {
      switch(pass)
      {
        case 1:
          glColor4f(1,1,1,0.5);
          glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
          //glEnable(GL_BLEND);
          glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 
          glEnable(GL_TEXTURE_2D);
          glBindTexture(GL_TEXTURE_2D,s.tex_ids[c]);
          break;
        default:
        case 0:
          glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
          glColor4f(0,0,0,1);
          break;
      }
      glBegin(GL_QUADS);
        glTexCoord2d(1,0);
        glVertex3f( 0.5*u(0),-0.5*u(1),0.5*u(2));
        glTexCoord2d(0,0);
        glVertex3f(-0.5*u(0),-0.5*u(1),0.5*u(2));
        glTexCoord2d(0,1);
        glVertex3f(-0.5*u(0), 0.5*u(1),0.5*u(2));
        glTexCoord2d(1,1);
        glVertex3f( 0.5*u(0), 0.5*u(1),0.5*u(2));
      glEnd();
      switch(pass)
      {
        case 1:
          glBindTexture(GL_TEXTURE_2D, 0);
          glDisable(GL_TEXTURE_2D);
          glDisable(GL_BLEND);
          break;
        default:
          break;
      }
    }

    glPopMatrix();
  }

  glDisable(GL_LIGHTING);
  glEnable(GL_COLOR_MATERIAL);
  glLineWidth(3.f);
  glColor4f(1,0,1,1);
  glutWireCube(0.25);
  glColor4f(1,0.5,0.5,1);
  //glutWireSphere(0.125,20,20);
  {
    glPushMatrix();
    glTranslated(0,-1,0);
    draw_floor();
    glPopMatrix();
  }
  
  // Axes
  for(int d = 0;d<3;d++)
  {
    glColor4f(d==0,d==1,d==2,1);
    glBegin(GL_LINES);
    glVertex3f(0,0,0);
    glVertex3f(d==0,d==1,d==2);
    glEnd();
  }

  glMatrixMode(GL_PROJECTION);
  glPopMatrix();
  glMatrixMode(GL_MODELVIEW);
  glPopMatrix();
  report_gl_error();

  if(render_to_texture)
  {
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, 0);
  }
}

void display()
{
  using namespace igl;
  using namespace std;
  using namespace Eigen;
  glClearColor(back(0),back(1),back(2),0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glEnable(GL_DEPTH_TEST);

  // Update aspect ratios (may have changed since undo/redo)
  {
    const double aspect = (double)width/(double)height;
    for(int c = 0;c<(int)s.cameras.size();c++)
    {
      auto & camera = s.cameras[c];
      auto & tex_id = s.tex_ids[c];
      auto & fbo_id = s.fbo_ids[c];
      auto & dfbo_id = s.dfbo_ids[c];
      if(aspect != camera.m_aspect)
      {
        cout<<"Initializing camera #"<<c<<"..."<<endl;
        camera.m_aspect = aspect;
        bool ret = init_render_to_texture(width,height,tex_id,fbo_id,dfbo_id);
        assert(ret);
      }
      draw_scene(camera,true,tex_id,fbo_id,dfbo_id);
    }
  }
  {
    auto & camera = s.cameras[s.viewing_camera];
    draw_scene(camera,false,0,0,0);
  }


  TwDraw();
  glutSwapBuffers();
  glutPostRedisplay();
}


void mouse_wheel(int wheel, int direction, int mouse_x, int mouse_y)
{
  using namespace std;
  using namespace igl;
  using namespace Eigen;
  GLint viewport[4];
  glGetIntegerv(GL_VIEWPORT,viewport);
  if(wheel == 0 && TwMouseMotion(mouse_x, viewport[3] - mouse_y))
  {
    static double mouse_scroll_y = 0;
    const double delta_y = 0.125*direction;
    mouse_scroll_y += delta_y;
    TwMouseWheel(mouse_scroll_y);
  }
  auto & camera = s.cameras[s.viewing_camera];
  switch(center_type)
  {
    case CENTER_TYPE_ORBIT:
      if(wheel==0)
      {
        // factor of zoom change
        double s = (1.-0.01*direction);
        //// FOV zoom: just widen angle. This is hardly ever appropriate.
        //camera.m_angle *= s;
        //camera.m_angle = min(max(camera.m_angle,1),89);
        camera.push_away(s);
        // Rotation should stay around at
      }else
      {
        // Dolly zoom:
        camera.dolly_zoom((double)direction*1.0);
      }
      break;
    default:
    case CENTER_TYPE_FPS:
      // Move `eye` and `at` 
      Vector3d diff = (wheel==0?Vector3d(0,0,1):Vector3d(-1,0,0))*0.1;
      camera.dolly(diff*direction);
      break;
  }
}

void mouse(int glutButton, int glutState, int mouse_x, int mouse_y)
{
  using namespace std;
  using namespace Eigen;
  using namespace igl;
  bool tw_using = TwEventMouseButtonGLUT(glutButton,glutState,mouse_x,mouse_y);
  switch(glutButton)
  {
    case GLUT_RIGHT_BUTTON:
    case GLUT_LEFT_BUTTON:
    {
      switch(glutState)
      {
        case 1:
          // up
          glutSetCursor(GLUT_CURSOR_INHERIT);
          is_rotating = false;
          break;
        case 0:
          if(!tw_using)
          {
            push_undo();
            glutSetCursor(GLUT_CURSOR_CYCLE);
            // collect information for trackball
            is_rotating = true;
            down_camera = s.cameras[s.viewing_camera];
            down_x = mouse_x;
            down_y = mouse_y;
          }
        break;
      }
      break;
      // Scroll down
      case GLUT_WHEEL_DOWN:
      {
        mouse_wheel(0,-1,mouse_x,mouse_y);
        break;
      }
      // Scroll up
      case GLUT_WHEEL_UP:
      {
        mouse_wheel(0,1,mouse_x,mouse_y);
        break;
      }
      // Scroll left
      case GLUT_WHEEL_LEFT:
      {
        mouse_wheel(1,-1,mouse_x,mouse_y);
        break;
      }
      // Scroll right
      case GLUT_WHEEL_RIGHT:
      {
        mouse_wheel(1,1,mouse_x,mouse_y);
        break;
      }
    }
  }
}

void mouse_drag(int mouse_x, int mouse_y)
{
  using namespace igl;
  using namespace std;
  using namespace Eigen;
  /*bool tw_using =*/ TwMouseMotion(mouse_x,mouse_y);

  if(is_rotating)
  {
    glutSetCursor(GLUT_CURSOR_CYCLE);
    auto & camera = s.cameras[s.viewing_camera];
    Quaterniond q;
    switch(rotation_type)
    {
      case ROTATION_TYPE_IGL_TRACKBALL:
      {
        // Rotate according to trackball
        igl::trackball(
          width,
          height,
          2.0,
          down_camera.m_rotation.conjugate(),
          down_x,
          down_y,
          mouse_x,
          mouse_y,
          q);
          break;
      }
      case ROTATION_TYPE_TWO_AXIS_VALUATOR_FIXED_UP:
      {
        two_axis_valuator_fixed_up(
          width,
          height,
          2.0,
          down_camera.m_rotation.conjugate(),
          down_x,
          down_y,
          mouse_x,
          mouse_y,
          q);
        break;
      }
      default:
        break;
    }
    camera.m_rotation = q.conjugate();
    switch(center_type)
    {
      default:
      case CENTER_TYPE_ORBIT:
        // at should be fixed
        //
        // at_1 = R_1 * t_1 - R_1 * z = at_0
        // t_1 = R_1' * (at_0 + R_1 * z)
        camera.m_translation = 
          camera.m_rotation.conjugate() * 
            (down_camera.at() + 
               camera.m_rotation * Vector3d(0,0,1) * camera.m_at_dist);
        assert((down_camera.at() - camera.at()).squaredNorm() < DOUBLE_EPS);
        break;
      case CENTER_TYPE_FPS:
        // eye should be fixed
        //
        // eye_1 = R_1 * t_1 = eye_0
        // t_1 = R_1' * eye_0
        camera.m_translation = camera.m_rotation.conjugate() * down_camera.eye();
        assert((down_camera.eye() - camera.eye()).squaredNorm() < DOUBLE_EPS);
        break;
    }
  }
}

void key(unsigned char key, int mouse_x, int mouse_y)
{
  using namespace std;
  int mod = glutGetModifiers();
  switch(key)
  {
    // ESC
    case char(27):
      rebar.save(REBAR_NAME);
    // ^C
    case char(3):
      exit(0);
    case 'z':
    case 'Z':
      if(mod & GLUT_ACTIVE_COMMAND)
      {
        if(mod & GLUT_ACTIVE_SHIFT)
        {
          redo();
        }else
        {
          undo();
        }
        break;
      }
    default:
      if(!TwEventKeyboardGLUT(key,mouse_x,mouse_y))
      {
        cout<<"Unknown key command: "<<key<<" "<<int(key)<<endl;
      }
  }
}


int main(int argc, char * argv[])
{
  using namespace std;
  using namespace Eigen;
  using namespace igl;

  // print key commands
  cout<<"[Command+Z]         Undo."<<endl;
  cout<<"[Shift+Command+Z]   Redo."<<endl;
  cout<<"[^C,ESC]            Exit."<<endl;

  // Init glut
  glutInit(&argc,argv);
  if( !TwInit(TW_OPENGL, NULL) )
  {
    // A fatal error occured
    fprintf(stderr, "AntTweakBar initialization failed: %s\n", TwGetLastError());
    return 1;
  }
  // Create a tweak bar
  rebar.TwNewBar("bar");
  TwDefine("bar label='camera' size='200 550' text=light alpha='200' color='68 68 68'");
  TwType RotationTypeTW = ReTwDefineEnumFromString("RotationType","igl_trackball,two_axis_fixed_up");
  rebar.TwAddVarRW("rotation_type", RotationTypeTW,&rotation_type,
    "keyIncr=] keyDecr=[");
  TwType CenterTypeTW = ReTwDefineEnumFromString("CenterType","orbit,fps");
  rebar.TwAddVarRW("center_type", CenterTypeTW,&center_type,
    "keyIncr={ keyDecr=}");
  rebar.load(REBAR_NAME);
  init_cameras();

  // Init antweakbar
  glutInitDisplayString( "rgba depth double samples>=8");
  // Top right corner
  glutInitWindowSize(glutGet(GLUT_SCREEN_WIDTH)/2.0,glutGet(GLUT_SCREEN_HEIGHT)/2.0);
  glutInitWindowPosition(glutGet(GLUT_SCREEN_WIDTH)/2.0,-1);
  glutCreateWindow("camera");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(key);
  glutMouseFunc(mouse);
  glutPassiveMotionFunc((GLUTmousemotionfun)TwEventMouseMotionGLUT);
  glutMotionFunc(mouse_drag);

  glutMainLoop();

  return 0;
}