Op 17/11/2020 om 22:12 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> The macro works perfectly... as long as your scene camera is situated
>> about the origin of the Y-axis.
> 
> For the moment, just disregard my other suggestions/guesses.
> 
> Just get rid of the VCorr term in the matrix.
> I have no idea what that's for, but it seems to be the source of the problem.
> 
> Do a few fast, simple [but extreme] renders and see what you think.
> 
> 

#declare NoFall =
transform {
   matrix < 1,     0,      0,
           ShearX, 1, ShearZ,
            0,     0,      1,
            0,     0,      0>
}

Better (the camera stays at the correct altitude) but is still shifted 
increasingly in the view direction. At least, it shows that, as 
suspected, VCorr did not serve any purpose. Interestingly, in its first 
version, John did not have a VCorr at all!

Using a cube as a proxy camera, shifted an arbitrary value in front of 
the camera to make it visible, I can show what happens. The red, 
transparant, box is the proxy of the "real" camera; the yellow box is 
the proxy of the "real" camera, shifted along the line of view after the 
application of the NoFall transform. The distance between the cubes 
increases with the height of the camera for y>0.

 From this, it is easy to write a quick-and-dirty correction to be added 
/after/ the NoFall transform in the camera definition:

//start code
   FieldCam (CamLoc, CamLookAt)
   #local ProxyCam =
   box {
     <-1, -1, -1>, <1, 1, 1>
     translate CamLoc
     transform {NoFall}
   }
   #local MinBox = min_extent(ProxyCam);
   #local MaxBox = max_extent(ProxyCam);
   #local MidPoint = ((MaxBox-MinBox)/2) + MinBox;
   #local CamLoc_corr = CamLoc - MidPoint;

#declare Camera =
#if (FC)
camera {
   perspective
   location  CamLoc
   sky       CamSky
   up        CamSky
   direction z*CamZoom
   right     x*AspectRatio
   angle     CamAng
   transform {NoFall}
   translate CamLoc_corr
   look_at   CamLookAt
}
#else
camera {
   perspective
   location  CamLoc
   sky       CamSky
   up        CamSky
   direction z*CamZoom
   right     x*AspectRatio
   angle     CamAng
   look_at   CamLookAt
}
#end

camera {Camera}
//end code

But this is not as elegant as finding a way to do this already in the 
macro ;-)

-- 
Thomas

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