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 CAD / Ray-Tracing / 2501
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Subject: 
Re: Is it possible to use LDView as POV-Ray previewer?
Newsgroups: 
lugnet.cad.ray
Date: 
Tue, 6 Dec 2005 17:29:32 GMT
Viewed: 
7499 times
  
In lugnet.cad.ray, Lars C. Hassing wrote:
Well, yes, but could you try generating these parameters in stead:
   location
   sky
   look_at
   angle
These should be adequate to fully describe the camera.
ldglite uses them http://ldglite.sourceforge.net/ldglitepov.html
and I have already made a -csky option.

I can do that.  Unless I'm badly mistaken, my existing up will work fine as a
sky vector.


My impression has always been that you should not tamper with
the up and right vectors, only for changing the aspect radio.
I have already added an option for aspect ratio that modifies
the right vector.

Reading between the lines of the descriptions of the various camera settings, it
really looks like POV-Ray automatically generates direction, up, and right based
on the other settings.  By providing them directly, you can ensure that you get
exactly what you're looking for.  It seems to me that all the various ways that
they allow you to specify the camera are done specifically to make it easier for
a human to place the camera.  The tutorials and documentation of the settings
all seem to be written based on the assumption that a human is figuring out the
camera position on their own.

I'm aware that the length of up/right defines the aspect ratio, but my up and
right vectors are both unit length, so the aspect ratio can be adjusted by
multiplying right by the aspect ratio.  (In fact, the POV-Ray code I spit out
for my testing defines ASPECT to 4/3, and puts ASPECT * <calculated right> in
the right vectory.  L3P does something similar in its current released form
(right = 4/3 * x).

Also, since you have to calculate which direction right faces when you allow the
camera to be twisted via the sky vector, it just seems to make more sense to
define these values directly.

So, if you could generate the sky vector that would be great.

Having said all of the above, it really sounds like sky and look_at can be
trivially calculated from the vectors I already have.  I'll make look_at the
location plus the direction, and assuming sky is just an up vector where the
length doesn't matter, I've already got that.

--Travis



Message is in Reply To:
  Re: Is it possible to use LDView as POV-Ray previewer?
 
(...) Well, yes, but could you try generating these parameters in stead: location sky look_at angle These should be adequate to fully describe the camera. ldglite uses them (URL) I have already made a -csky option. My impression has always been that (...) (19 years ago, 6-Dec-05, to lugnet.cad.ray)

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