Le 18-02-10 à 19:47, Mike Horvath a écrit :
> What effect does scaling a camera have on focal_blur?
> 
> I have two cameras, and they should both produce the same result. But 
> they don't.
> 
> 
> 
> // focal blur camera
> camera {
>    location  <0,0,-5>
>    look_at   <0,0,0>
>    right     x*image_width/image_height
>    up y
>    aperture 1.0           // [0...N] larger is narrower depth of field 
> (blurrier)
>    blur_samples 10        // number of rays per pixel for sampling
>    focal_point <0,0,0>    // point that is in focus <X,Y,Z>
>    confidence 0.95        // [0...<1] when to move on while sampling 
> (smaller is less accurate)
>    variance 1/200         // [0...1] how precise to calculate (smaller 
> is more accurate)
>    scale 2
> }
> 
> /*
> // focal blur camera
> camera {
>    location  <0,0,-10>
>    look_at   <0,0,0>
>    right     x*image_width/image_height
>    up y
>    aperture 1.0           // [0...N] larger is narrower depth of field 
> (blurrier)
>    blur_samples 10        // number of rays per pixel for sampling
>    focal_point <0,0,0>    // point that is in focus <X,Y,Z>
>    confidence 0.95        // [0...<1] when to move on while sampling 
> (smaller is less accurate)
>    variance 1/200         // [0...1] how precise to calculate (smaller 
> is more accurate)
> }
> */

The amount of focal blur depends on the ratio between (1) the distance 
between the camera's location and the focal point location and (2) the 
actual aperture.

So, with everything else been the same, the second camera have twice the 
focal length for the same aperture, resulting in half the focal blur or 
twice the sharpness depth.

To get the same results, you need to scale the aperture by the same 
amount as the rest of the camera use for the second camera :
aperture 2.0


Alain

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