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Let me offer some information on what I'm trying to do:
I want to know the specifics of focal_blur operation, to better
emulate images from a 35mm camera. Once I can emulate the 35mm camera,
I should be able to blend a photograph with a POV rendering, and have
the perspectives and general appearance of the two images match each
other.
Well, I should mention that I'm not trying to account for any lens
abberations yet. For now, I'm just trying to match a POV camera to an
"idealized" 35mm camera. So far, I think I've got the angle of view
and aspect ratio concepts figured out. My next goal is to try and
match depth of field settings between the two systems.
So far, I have the following camera defined:
///////////////////////////////////////////////////////////
#declare CPos = <0,0,0>; // Camera Position
#declare SPos = <-3,7,13>; // Subject Position
#declare SD = vlength(CPos,SPos); // Subject Distance
#declare FL = 50; // Focal Length, in mm
#declare Ix = 36; // Film Width, in mm
#declare Iy = 24; // Film Height, in mm
#declare Mag = FL/(SD-(FL*2)); // Magnification
camera { perspective
right x*Ix / FL*(Mag+1)
up y*Iy / FL*(Mag+1)
location CPos
look_at SPos
#if(Use_Blur=1)
aperture 5
blur_samples 32
focal_point SPos
confidence 0.99
variance 1/255
#end
}
///////////////////////////////////////////////////////////
First, can someone confirm that the camera "location" value is
actually jittered, while ALL other dimensions and parameters are held
constant, to produce the focal_blur? If the jittering temporarily
modifies the values of any of the other parameters, please let me know
which ones and how.
Second, I assume that the "aperture" value DIRECTLY specifies the
magnitude of the RADIUS (not diameter) of the jittering, as measured
in POV-Units. Is this correct?
Third, is the array of jittered camera locations arranged in a square
grid, or is it arranged in an approximate circular pattern? I've been
assuming square, but circular would better approximate a typical lens.
Finally, if anyone spots any errors in the 35mm camera emulation I
have listed above, please let me know. I *think* what I have so far is
a fairly accurate emulation, but I might also have overlooked some
details. Please let me know if I have.
Later,
Glen
7no### [at] ezwv com (Remove the numeral "7")
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"Glen Berry" <7no### [at] ezwvcom> wrote:
> First, can someone confirm that the camera "location" value is
> actually jittered, while ALL other dimensions and parameters are held
> constant, to produce the focal_blur?
Thats what I assume, ...
> Second, I assume that the "aperture" value DIRECTLY specifies the
> magnitude of the RADIUS (not diameter) of the jittering, as measured
> in POV-Units. Is this correct?
... this too, but I haven't had a look at the code yet, so I can't confirm ...
> Third, is the array of jittered camera locations arranged in a square
> grid, or is it arranged in an approximate circular pattern? I've been
> assuming square, but circular would better approximate a typical lens.
This can be confirmed at least for 3.1 POV (I don't think it has changed
in 3.5 yet), as you can see yourself in a scene like this: put one single
small sphere between the focal-point and the cam-location. use a quite big
aperature, and you will see, that the object appears as a square ...
this leads to the conclusion, that the jitter doesn't happen in a circular
manner, but will probably be to the same amounts in x-y-z direction ...
> Finally, if anyone spots any errors in the 35mm camera emulation I
> have listed above, please let me know. I *think* what I have so far is
> a fairly accurate emulation, but I might also have overlooked some
> details. Please let me know if I have.
looks good so far ...
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in news:Y=jrPEh5upqZ+VuOysTVd5zUAMGp@4ax.com Glen Berry wrote:
> I want to know the specifics of focal_blur operation, to better
> emulate images from a 35mm camera.
Not an awnser to your questions, but the macro on this page may be of some
help:
http://www.wozzeck.net/images/DoF.html
Ingo
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