Subject:
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Re: LDGLite orientation matrix (l3p enhancement requests?)
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Newsgroups:
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lugnet.cad.dev, lugnet.cad.ray
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Date:
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Fri, 25 Jan 2002 01:50:07 GMT
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Viewed:
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184 times
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On January 18th Don Heyse wrote...
> ... But you're missing the point.
> I'm trying to position ldglite as a cheesy scene modeler for l3p (well
> actually Jacob asked for it). I don't just want a good view. I want
> an identical view. So I don't want l3p to do *any* of the camera
> positioning. Look here to see where I'm going with this:
>
> http://ldglite.sourceforge.net/ldglitepov.html
>
> I *know* you want to do this with l3lab someday so why not just add a
> few harmless command line options to l3p now. :-) After all, what's
> the harm in passing the orthographic command through but ignoring it
> in your camera calculations?
Right, point taken. I don't know when I will get the time for an L3Lab overhaul.
You seem to have done pretty well in ldglite so far,
so let me know what you want.
> > > 2. I could also use a way to set the sky vector on the command line.
> >
> > L3P doesn't support tilting the camera (yet :-), simply because I estimated
> > it a rare feature. I don't think I have gotten any requests either.
> > BTW see http://www.spiritone.com/~english/cyclopedia/sky.html
>
> I'm not sure how you can say you don't support tilting the camera.
> What's the default sky vector when I specify a camera location and
> look_at point on the l3p command line that aren't in the same y plane?
I think the sky vector is the *initially* upward direction of the camera:
POV 3.1 doc says:
4.4.1.2 The Sky Vector
Normally POV-Ray pans left or right by rotating about the y-axis
until it lines up with the look_at point and then tilts straight up or down
until the point is met exactly. However you may want to slant the camera
sideways like an airplane making a banked turn. You may change the tilt
of the camera using the sky vector. For example:
camera {
location <3,5,-10>
sky <1,1,0>
look_at <0,2,1>
}
This tells POV-Ray to roll the camera until the top of the camera is in line
with the sky vector. Imagine that the sky vector is an antenna
pointing out of the top of the camera. Then it uses the sky vector
as the axis of rotation left or right and then to tilt up or down in line
with the sky until pointing at the look_at point. In effect you're telling
POV-Ray to assume that the sky isn't straight up. Note that the sky vector
must appear before the look_at vector.
The sky vector does nothing on its own. It only modifies the way
the look_at vector turns the camera. The default value is sky<0,1,0>.
(end quote)
This is also how I understand the example in
http://www.spiritone.com/~english/cyclopedia/sky.html
> If I put the camera location directly above the look_at point, what's
> the default sky vector?
Well, yes, it could be any direction...
> > > 3. It'd be handy to set PCT on the command line, but if this is too much
> > > of a chore I can continue to scale by moving the camera location.
> >
> > You can by using the -cg option. If the third parameter is negative,
> > its absolute value is used as PCT.
> > But I may add another option to use together with the -cc option.
>
> That'd be nice, since I want to use the -cc option.
The PCT was primarily thought of as an shortcut to move the camera
when hand-editing the POV file.
Do you think it make sense to specify both -cc, -cla and -cpct ?
/Lars
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