POV-Ray : Newsgroups : povray.newusers : sphere proportions : Re: sphere proportions Server Time
19 Jun 2021 20:51:40 EDT (-0400)
  Re: sphere proportions  
From: Bald Eagle
Date: 1 Jun 2021 19:00:00
Message: <web.60b6bb31dfb9240b1f9dae3025979125@news.povray.org>
Yeah, but the exact syntax of those commands is more like:

camera {
 location <0, 0, -3>
 look_at <0, 0, 0>
 right x*image_width/image_height

Dunno which version you're landing on, but the most up-to-date documentation
will be at:

I don't know if this will help or not, but consider this:

There is no sphere.
Likewise, there is no camera, no light - none of it exists.
It's all just one big mathematical simulation whose whole goal is to do one
thing - figure out what color to make that pixel at the current <x, y> location.
(Not on the screen, mind you - in a FILE - a big wad of 0's and 1's that might
have visual meaning when properly processed and displayed on your monitor.


As such, you have no space, and no reference by which to establish an objective
unit of measure.  And so at some point you have to boot-strap things and impose
one "arbitrarily".
And that is done by the standard method of taking the image dimensions and
making it one unit high and one unit wide in the z=1 plane for the default
(you don't even have to declare a camera if you use the default and know that
it's at the origin and looking at <0, 0, 1>)
But now you have to take the number of pixels into account, and - adjust - for

Take a piece of regular letter/A4 paper and divide it into 10 units long and 10
units wide - you get rectangles.   It gets farther off if you use 8.5 x 14.
So if you were going to use sin and cos to calculate the positions of points
around the circle, and you just graphed it as is - it would _look_ like an
ellipse because your basis vectors are unequal.  So instead of applying a
correction to every bloody thing that you do, you could just view the paper
through a lens that scrunched the paper in one dimension, altering the visual
perception of the graph such that it now properly _looks_ like a circle.

And that's the all the "camera" is in POV-Ray, a mathematical "lens" that maps
the raw mathematical result onto a different "space".

And truly, unless you have some specific need for knowing HOW it all works
(believe me, I understand), then just don't worry about it and plug-and-chug.


Post a reply to this message

Copyright 2003-2021 Persistence of Vision Raytracer Pty. Ltd.