[vtkusers] how to know image scale from camera distance....

Amey amay.ms at gmail.com
Wed Jan 14 04:42:09 EST 2015

I have a large 2D image. To show it initially, I set the camera distance and
focal point such that the image appears fit to screen. I do this as below:

double centerX = imageWidth/2.0;
double centerY = imageHeight/2.0

camera.setFocalPoint( centerX , centerY, 0);
double angle = math.RadiansFromDegrees( camera.GetViewAngle() );
double distance = Math.max(centerX, centerY)/ Math.tan( angle * 0.5 );
camera.setPosition( centerX, centerY, distance);

This shows the image correctly fit to screen.

Now I have to display the scale of the image. So, I want to calculate the
currently visible image scale based on the distance of the camera.
Can you help me how to determine it?

Thanks a lot for your help,

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