callendorph nous illumina en ce 2008-07-17 12:47 -->

> I understand what you are saying in terms of controlling the camera's field of
> view with angle and controlling with a camera matrix transform, but the field
> of view of the camera is only a means to an end for me. What I really want to
> quantify, is the width of a single pixel in an image of a known resolution. So
> from what it seems to me, is that I can use the direction vector to contol the
> "focal length" of the camera, and the right/up vectors to create the
> appropriate field of view. Now the thing I am having trouble understanding is
> how to convert this image plane into width and height of the image in Povray
> standard units. From this I should be able to use the resolution to calculate
> how big a pixel is in terms of these "Povray units." Does this make sense?
> Does the right and up vector actually control the size of this image plane? If
> so then I should be able to set
> camera {
> location = <0,0,0>
> right = 1*x
> up = (img_height/img_width)*y
> direction = 0.5*z
> }
> This , in theory would give me an image plane with dimensions 1 units x 0.75
> units for an aspect ratio of 1.333. From here then, I should be able to divide
> the width (1unit) by 640 and get the "pixel width" of each pixel in the image.
> Does it work this way, or am I completely missing the mark?
> 
> Thanks for all your help,
> ~Carl
> 
> 
The width in unit of a pixel at a given resolution depends on at least two 
things: The field of view AND the distance of the object from the camera. As the 
distance between any object and the camera change from object to object, and 
even for a given object, in any image you can have 1 pixel that covers 0.001 
unit next to one that covers 100 units, or even more.
What you can calculate is the angular width of a pixel.

-- 
Alain
-------------------------------------------------
I believe that banking institutions are more dangerous to our liberties than
standing armies. Already they have raised up a monied aristocracy that has
set the government at defiance. The issuing power should be taken from the
banks and restored to the people to whom it properly belongs.
Thomas Jefferson

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