Subject:
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Re: Can LDGLite print the current orientation matrix? (feature request)
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Newsgroups:
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lugnet.cad.dev
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Date:
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Thu, 17 Jan 2002 23:41:26 GMT
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Viewed:
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897 times
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Don Heyse wrote...
> [snip], but I don't completely understand the
> STEREO stuff in the location part of an l3p camera setting. Can you
> or somebody explain it? I can create an ordinary location line like
> this:
>
> location <cx,cy,cz> +PCT/100.0*<dx,dy,dz>
>
> where <cx,cy,cz> is the camera location and <dx,dy,dz> is the distance
> from the camera to the look_at point, but l3p adds that STEREO part and
> that's where I get lost.
>
> location vaxis_rotate(<cx,cy,cz> +PCT/100.0*<dx,dy,dz>,
> <ax,ay,az>,STEREO)
If STEREO is zero (the default), then there's no rotation, and it's the same as
location <cx,cy,cz> +PCT/100.0*<dx,dy,dz>
> According to the POV docs <ax,ay,az> is an axis (through the origin?)
> and STEREO is the number of degrees to rotate about that axis. Fine,
> but how does this work, since I'm not necessarily looking at the
> origin with the look_at statement. Am I missing something? Help!
No, *I* seem to have missed something...
It takes four numbers to determine a vector in space, so <ax,ay,az> must
obviously be through origin. Because I usually build my models around origin
(it worked best like that with LEdit/LDraw) I didn't notice the error while testing...
You have to translate the look_at point to the origin before rotating the location
around the vector (the vector is perpendicular to the location-look_at and lies
in the sky - location-look_at plane)
The camera definition in the coming was already under revision to become
more readable (I hope), and I have now corrected the stereo part:
camera {
#declare PCT = 0; // Percentage further away
#declare STEREO = 0; // Normal view
#declare L3BetweenEyes = 1/12; // Distance between eyes (stereo cameras) typically 1/12 of distance to model
//Uncomment either two lines below to make stereo images
//#declare STEREO = -degrees(atan2(L3BetweenEyes,1))/2; // Left view
//#declare STEREO = degrees(atan2(L3BetweenEyes,1))/2; // Right view
#declare L3Location = <42.2688,-38.6915,-42.2688>;
#declare L3LookAt = <0.251318,-4.38439,-0.251318>; // Calculated (not -cla)
#declare L3Location = L3Location + PCT/100.0*(L3Location-L3LookAt);
#if (STEREO = 0)
location L3Location
#else
location L3LookAt + vaxis_rotate(L3Location-L3LookAt, <-0.353553,-0.866025,0.353553>, STEREO)
#end
sky -y
right -4/3*x
look_at L3LookAt
angle 67.3801
rotate <0,1e-5,0> // Prevent gap between adjecent quads
//orthographic
}
BTW: Google gave this great link on vaxis_rotate:
http://www.spiritone.com/~english/cyclopedia/vaxis.html
/Lars
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