Charles Krause wrote:
> 
> Here's something I'd like to do with a camera, and I havn't got a clue how.
> 
> What I'd like to do is to set the camera, and the image so that the bounding
> box of an object fills the field of view completely. This if the object
> _was_ a box, the side of the box would fill the image, the WHOLE side of the
> box would show, and NOTHING else would show.
> 
> any ideas?

Disclaimers: #1. This solution uses functions found in MegaPOV...
although they are among the features most likely to appear in the
next generation of POV-Ray, this code will not run in standard
POV 3.1. If you insist on using only standard POV code, you'll
have to manually supply the corners of the bounding box. If you
aren't familiar with MegaPOV, min_extent() returns the lower
corner of the bounding box, while max_extent() returns the upper
corner of the bounding box. You have to mentally substitute your
hand supplied corners.
#2. What you're asking to do (a sort of "zoom extents" camera)
is somewhat angle dependant (we are, afterall, talking about a
bounding *box*. So in order to get the image filled *completely* 
like you've described using this method, you kind of half to look
head on from one of the axial directions, AND match the
height/width ratio of the camera to the height width ratio of
the box as seen from that direction, however, this will give you
some ideas to get started. In fact, this is more likely to ensure
you get the closest view that completely includes the full extents
of the object, but you'll get the idea from this.
#3. This code was written quickly, and I don't guarantee it works
completely without modification in all situations. Take it as a
starting point only.
--------------------------------------------------------------------
#macro AngleBetween(V1,V2)
/* Calculates the angle between two vectors using the law of cosines -
   A good multipurpose function...
*/
    #local SA = vlength(V1);
    #local SB = vlength(V2);
    #local SC = vlength(V2-V1);
    
    #if ( SA>0 & SB>0 )
       #local T = degrees( acos ( (SA*SA+SB*SB-SC*SC)/(2*SA*SB) ));
    #else
       #local T = -1; //generic return meaning failure of function
    #end

    T
#end//end macro AngleBetween

#macro ZoomCam(objTarget,LocationPoint)
/*Given an object and the point of view to look from, define a camera
that 
  zooms in on it... 
*/
    #local LookAtPoint =
(max_extent(objTarget)+min_extent(objTarget))/2;
    #local LocalizedMax = max_extent(objTarget)-LocationPoint;
    #local LocalizedMin = min_extent(objTarget)-LocationPoint;
    #local CamAngle = AngleBetween(LocalizedMax,LocalizedMin);

    #if (CamAngle != -1 )
    camera {
	location LocationPoint
        look_at LookAtPoint 
        angle CamAngle
    }
    #else
        #warning "Warning: Degenerate bounding or bad cam angle... 
                  unable to compute camera\n"
    #end
#end//end Zoomcam Macro

//now apply the macro...
#declare SomeObject = 
   sphere { 0,1 pigment { rgb<0,0,1> } finish { phong 1 }}

ZoomCam(SomeObject,<0,0,-10>)
light_source { <200,200,-200> color rgb 1 }
object {SomeObject }

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