[vtkusers] Error in vtkRenderer::ResetCamera

[Scott Johnson]

Hello Folks,

 

I'm new to VTK and was trying to figure out some clipping issues in
vtkRenderer.  While poking around in the code I ran across
vtkRenderer::ResetCamera and a potential coding error.  It seems that
'vn' is never initialized prior to being used.  I'll include the code
for the method.  (I just checked out a new version from the HEAD of the
cvs repository.)

 

I also added a comment and a possible fix.

 

I'd be interested to hear if this a real problem or if I'm just
imagining it.

 

Thanks

 

            -- Scott

 

void vtkRenderer::ResetCamera(double bounds[6])

{

  double center[3];

  double distance;

  double vn[3], *vup;

 

  this->GetActiveCamera();

  if ( this->ActiveCamera != NULL )

    {

    this->ActiveCamera->GetViewPlaneNormal(vn);

    }

  else

    {

    vtkErrorMacro(<< "Trying to reset non-existant camera");

    return;

    }

 

  center[0] = (bounds[0] + bounds[1])/2.0;

  center[1] = (bounds[2] + bounds[3])/2.0;

  center[2] = (bounds[4] + bounds[5])/2.0;

 

  double w1 = bounds[1] - bounds[0];

  double w2 = bounds[3] - bounds[2];

  double w3 = bounds[5] - bounds[4];

  w1 *= w1;

  w2 *= w2;

  w3 *= w3;

  double radius = w1 + w2 + w3;

 

  // If we have just a single point, pick a radius of 1.0

  radius = (radius==0)?(1.0):(radius);

 

  // compute the radius of the enclosing sphere

  radius = sqrt(radius)*0.5;

 

  // default so that the bounding sphere fits within the view fustrum

 

  // compute the distance from the intersection of the view frustum with
the

  // bounding sphere. Basically in 2D draw a circle representing the
bounding

  // sphere in 2D then draw a horizontal line going out from the center
of

  // the circle. That is the camera view. Then draw a line from the
camera

  // position to the point where it intersects the circle. (it will be
tangent

  // to the circle at this point, this is important, only go to the
tangent

  // point, do not draw all the way to the view plane). Then draw the
radius

  // from the tangent point to the center of the circle. You will note
that

  // this forms a right triangle with one side being the radius, another
being

  // the target distance for the camera, then just find the target dist
using

  // a sin.

  double
angle=vtkMath::RadiansFromDegrees(this->ActiveCamera->GetViewAngle());

  double parallelScale=radius;

  

  this->ComputeAspect();

  double aspect[2];

  this->GetAspect(aspect);

  

  if(aspect[0]>=1.0) // horizontal window, deal with vertical
angle|scale

    {

    if(this->ActiveCamera->GetUseHorizontalViewAngle())

      {

      angle=2.0*atan(tan(angle*0.5)/aspect[0]);

      }

    }

  else // vertical window, deal with horizontal angle|scale

    {

    if(!this->ActiveCamera->GetUseHorizontalViewAngle())

      {

      angle=2.0*atan(tan(angle*0.5)*aspect[0]);

      }

    

    parallelScale=parallelScale/aspect[0];

    }

 

  distance =radius/sin(angle*0.5);

 

  // check view-up vector against view plane normal

  vup = this->ActiveCamera->GetViewUp();

  //  SHOULD THIS NEXT LINE BE ADDED???

  // vn = this->ActiveCamera->GetViewPlaneNormal();

 

  if ( fabs(vtkMath::Dot(vup,vn)) > 0.999 )

    {

    vtkWarningMacro(<<"Resetting view-up since view plane normal is
parallel");

    this->ActiveCamera->SetViewUp(-vup[2], vup[0], vup[1]);

    }

 

  // update the camera

  this->ActiveCamera->SetFocalPoint(center[0],center[1],center[2]);

  this->ActiveCamera->SetPosition(center[0]+distance*vn[0],

                                  center[1]+distance*vn[1],

                                  center[2]+distance*vn[2]);

 

  this->ResetCameraClippingRange( bounds );

 

  // setup default parallel scale

  this->ActiveCamera->SetParallelScale(parallelScale);

}

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20091124/bff01aca/attachment.htm>