[Bf-committers] Re: Depth of field

[Guillermo S. Romero / Familia Romero]

matt@mke3.net (2003-07-14 at 1719.59 +1000):

<rantish>
> DOF doesn't just work by progressively blurring along a linear scale. The

Hehe, and proper DoF is not just blur either, it is sample
displacement (the reason you get "hidden" areas that othwerwise do not
appear). But he does not seem to like the jitter algo, so does not
matter.

> overlapping 'circles of confusion' converge over an initially steep curve, and
> then flatten out in a logarithmic-looking curve after the focus point. There are
> some good graphs that explain this process for different f-stops etc. here:
> http://www.renderman.org/RMR/Examples/dof/

IIRC one of the nice things of using a REYES renderer was that
DoF and other effects required just a small extra to get proper
results.
</rantish>

> An alterative to these 'front distance/back distance' settings is to use an
> 'aperture' setting. We already have a 'lens' (focal length) button for the
> camera, so the DOF could be derived from the aperture, focal length and shutter
> speed (FPS?).

Not FPS. Still images do not have FPS and probably no one sets that
value in that case (and imagine if you want 2s, that is .5 FPS).

FPS only dictates how many shots per second, but each shot can have a
wide range of times. Default film cameras use a .5 frame (180 deg of
shutter) as time (24 FPS -> 1/48 s), but it can be lowered in some
models. For video cameras it can be changed too (and maybe even a
wider range than film ones, but I have not checked).

So if you want to immitate cameras, you have to include shutter speed
(can be computed from MBlur and FPS, but complex for the user and
limited ranges, IMHO, better add or replace) and aperture (nothing I
can find). And to add more complexity, there is exposure in world
buttons (range .2 - 5, seems to work like going up or down a couple of
f-stops).

Some clean up and clarification would be nice, indeed.

GSR