Re: [Plib-devel] Bug with sign of pitch?

[Curtis L. O. <cu...@me...>]

Last I looked I didn't see anything like this, but what I would really
like is some code that would take a directional vector and an up
vector and translate this into an ssg XYZ - HPR coord structure.

What I'd like to use this for is given I know my camera position, and
the position of something I want centered on the screen, I want to
look directly at it (with control over the up direction.)  For
example, a chase plane view in a flight sim.

It's probably a simple thing to impliment, but I just haven't had a
chance to sit down and think it through ... and if someone has already
done the work I'd happily use that. :-)

Regards,

Curt.

Wolfram Kuss writes:
> BTW, I game developers might use this code as well.
> I use it for camera-movement (when I do a "make object fully
> visible").
> Its quite simple, but perhaps you want to put it into plib?
> 
> Here is the function:
> 
> --------------------- cut ------------------------------
> void /*sg*/Vec3fromHPR ( sgVec3 vec3, const sgVec3 hpr ) 
> // If hpr are the hpr of the camera, then this function gives the
> normalised
> // viewing direction. Of course roll is lost in this conversion.
> {
>   double ch, sh, cp, sp; 
> 
>   if ( hpr[0] == SG_ZERO )
>   {
>     ch = SGD_ONE ;
>     sh = SGD_ZERO ;
>   }
>   else
>   {
>     sh = (SGfloat) sin( (double)( hpr[0] * SG_DEGREES_TO_RADIANS )) ;
>     ch = (SGfloat) cos( (double)( hpr[0] * SG_DEGREES_TO_RADIANS )) ;
>   }
> 
>   if ( hpr[1] == SG_ZERO )
>   {
>     cp = SGD_ONE ;
>     sp = SGD_ZERO ;
>   }
>   else
>   {
>     sp = sin( (double)( hpr[1] * SG_DEGREES_TO_RADIANS )) ;
>     cp = cos( (double)( hpr[1] * SG_DEGREES_TO_RADIANS )) ;
>   }
>   vec3[0] = (SGfloat)( -sh * cp ) ;
>   vec3[1] = (SGfloat)( ch * cp ) ;
>   vec3[2] = (SGfloat)(  sp ) ;
> // rest is check
>   sgVec3 hprCheck;
>   sgHPRfromVec3 ( hprCheck, vec3) ;
>   if(0.01<abs(hprCheck[0]-hpr[0]))
>     fprintf(stderr,"\n*** Heading: %f vs %f***\n",hprCheck[0],hpr[0]);
>   if(0.01<abs(hprCheck[1]-hpr[1]))
>     fprintf(stderr,"\n*** Pitch: %f vs %f ***\n",hprCheck[1],hpr[1]);
>   
> 
> }
> --------------------- cut ------------------------------
> 
> Bye bye,
> Wolfram Kuss.
> 
> 
> _______________________________________________
> plib-devel mailing list
> pli...@li...
> http://lists.sourceforge.net/mailman/listinfo/plib-devel

-- 
Curtis Olson   Human Factors Research Lab       Flight Gear Project
Twin Cities    cu...@hf...                cu...@fl...
Minnesota      http://www.menet.umn.edu/~curt   http://www.flightgear.org