"udyank" <nomail@nomail> wrote:
> I need a bit of help with the focal blur module. I am trying to render a simple
> scene with 3 vertical bars in the front and 3 horizontal ones at the back. I'm
> having trouble with setting the focal length in the scene (focal_point does not
> seem to work for this). All the scene parameters (for eg. distances of objs from
> camera, their thickness etc.) are in terms of focal length. How do I set it as a
> param and use it to define all other distances? Also generally aperture in
> cameras is defined as a fraction of 'f'. How does the aperture param in POVRay
> correspond to real apertures defined as such?
>
> Another doubt: As I am trying to increase the aperture and putting my
> focal_point on the vertical bars in the front (ref: images in the ZIP), the bars
> at the back start "splitting" into parts. Any thoughts on how this could be
> happening?

You probably just need to improve the quality. Try using keywords  variance
with a value of 0.005 or less and  confidence  of 0.9 or more. And more
blur_samples, something like 100 or more.

I don't know much of anything about the workings of camera blur but my guess
would be the scene distances might play a big part in how the focus, or
aperture, is affected. Or vice versa. In other words, perhaps large focal_point
distances from camera location require larger aperture values to compensate.

However, from what I tried just now with it, I can't be sure there's a possible
correlation with enough to formulate what you're wanting to do. And yet there
might be something to do with scene size possible if you can constrain all
objects within a certain area of view. Distance from camera and its focal point
seem to make aperture require larger or smaller values, so if far away
focal_point then aperture increased could help.
Closer together and aperture must be smaller. I would only be guessing here, of
course, but that's what I was finding in my test scene.

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