On 2/11/2018 11:11 PM, Kenneth wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
> 
>>
>> Using your 'scale 2' camera, what it looks like is that the focal_blur's
>> focal_point of <0,0,0> (the focal 'plane')is actually shifting to <0,0,-5>. In
>> other words, it's keeping the same original 5-unit distance from the CAMERA--
>> not scaling to 2*5 = 10-units. That's what I see from a simple test, anyway.
> 
> .... and changing the focal_point to <0,0,5> does indeed bring the focal plane
> back to the original <0,0,0>.
> 
> Although, for a camera position that's not just <0,0,0> but something like
> <3,13,-9>, it appears that the interplay between scaled camera and 'new' focal
> plane gets much more complicated.
> 
> But I tried something weird, which seems to work(!) ...
> 
> The initial simple test:
> original camera position: <0,0,-5>
> original focal_point: <0,0,0>
> 
> With scale 2:
> new camera position: <0,0,-10>
> new focal_point set to: <0,0,5>
> 
> Now, with a more complicated camera position:
> original camera position: <3,13,-9>
> original focal point: <0,0,0>
> 
> With scale 2:
> new camera position: <...? ...> (I'm too lazy to figure it out)
> new focal_point set to: <-13,-3,9>
> 
> That appears to bring the original 'focal plane' of <0,0,0> back into sharp
> focus! (Although, that plane is always perpendicular or orthogonal(?) to the
> camera view.) The math for the new focal_point looks to be quite simple as well.
> 
> 
> 
> 
> 
> 

Thanks! That means:

     #local NewCameraFocalPoint = -1 * OldCameraLocation * 
(NewCameraScale - 1);

But is this only true if the OldCameraFocalPoint is <0,0,0>? What 
happens when the OldCameraFocalPoint is <5,20,-1>?

Would it be more intuitive if the focal point location automatically 
scaled scaled with the camera position? E.g.

     #local NewCameraFocalPoint = OldCameraFocalPoint * NewCameraScale;


Mike

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