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gregjohn wrote:
> Alain <ele### [at] netscapenet> wrote:
>> For a "default" camera where the right vector have been changed, the
>> horizontal field of view don't change with the right vector. The
>> direction vector can be used to change the angle of the field of view.
>> In early versions, before the angle keyword was introduced, it was
>> the only way to change the field of view.
>>
>> The up and right vectors determine the aspect ratio. They work by changing the
>> vertical field of view.
> 
> 
> Okay, yes, they change the aspect ratio, and they can mess it up by giving you a
> scenario where circles are not circular if you're not using 4x3 pixel ratio.
> 
> So, I'm doing:
> 
>  right x*1.33
>  up image_height/image_width*y*1.33
> 
> Now, regardless of what I do with the +H and +W switches, circles will be
> circular.   The problem is I may want to change the angle at some time. With
> the above code, I *can* change the horizontal field of view with:
> 
> 
>  right x*the_right
>  up image_height/image_width*y*the_right
> 
> where I plug in a number for "the_right".   I guess I'm looking for a good
> camera definition, a graphical image of what all the vectors mean in the
> default camera.  The one at
> 
> http://www.povray.org/documentation/view/3.6.1/246/
> 
> is completely lacking for the definition of a default camera.  Is 1.33 the x
> distance seen at the plane <0,0,1>???
> 
	The relation between angle and right is:
tan (angle/2) = ||right|| / (2 * ||direction||)

	(note that it is given in the page you pointed to).

	Moreover, direction is ||look_at - location|| / 2

		Jerome
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http://jeberger.free.fr
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