Ok, thanks so far for your help.
I understand (hopefully) most of what you have said.
But I think it needs to be calculated the other way round.
Field of view is a given (fixed) value (maybe changeable elsewhere) and based of the bounding box I need to find the distance to this bounding box by a calculation. The camera will be only zoomed on a dedicated line. By doing this I have always the same point from which i look at the model.
I understand (hopefully) most of what you have said.
But I think it needs to be calculated the other way round.
Field of view is a given (fixed) value (maybe changeable elsewhere) and based of the bounding box I need to find the distance to this bounding box by a calculation. The camera will be only zoomed on a dedicated line. By doing this I have always the same point from which i look at the model.