mm->vox integers per AFNI controller window user INPUT

gistfile1.txt

AFNI controller window user INPUT
------------------------------------------------
Appears to use implicit casting + boundary handling to create integer voxel
coordinates from the user-specified mm coordinates in the "Jump to (xyz)" box:


In afni.c , typical use of AFNI_jumpto_dicom() calls AFNI_jumpto_dicom_OLD(),
which converts user-provided mm coordinates to integer voxel coordinates in
three steps:

	1) uses THD_dicomm_to_3dmm() to get floating-point voxel (not mm) coordinates from image (anat_now)
	2) uses THD_3dmm_to_3dind() to turn those floating-point "index coordinates" to integer index coordinates (iv.ijk)
		- includes truncation via implicit cast
		  (because iv.ijk is just integers per typedef struct { int ijk[3] ;      } THD_ivec3 ; )
	3) pulls integers coordiantes ii, jj, and kk respectively from integer vector iv.ijk

Those three steps are invoked in this afni.c function: 

	 9811 int AFNI_jumpto_dicom_OLD( Three_D_View *im3d , float xx, float yy, float zz )
	 9812 {
	 9813    THD_dataxes  *daxes ;
	 9814    THD_fvec3 fv ; THD_ivec3 iv ;
	 9815    int ii,jj,kk ;
	 9816 
	 9817 ENTRY("AFNI_jumpto_dicom_OLD") ;
	 9818 
	 9819    LOAD_ANAT_VIEW(im3d) ;  /* 02 Nov 1996 */
	 9820 
	 9821    fv = THD_dicomm_to_3dmm( im3d->anat_now , TEMP_FVEC3(xx,yy,zz) ) ;
	 9822    iv = THD_3dmm_to_3dind ( im3d->anat_now , fv ) ;
	 9823    ii = iv.ijk[0] ; jj = iv.ijk[1] ; kk = iv.ijk[2] ;
	 9824 
	 9825    daxes = CURRENT_DAXES(im3d->anat_now) ;
	 9826    if( ii >= 0 && ii < daxes->nxx &&
	 9827        jj >= 0 && jj < daxes->nyy && kk >= 0 && kk < daxes->nzz ){
	 9828 
	 9829       AFNI_set_viewpoint( im3d , ii,jj,kk , REDISPLAY_ALL ) ; /* jump */
	 9830       RETURN(1) ;
	 9831    } else {
	 9832       BEEPIT ; WARNING_message("Jumpto DICOM failed -- bad coordinates?!") ;
	 9833       RETURN(-1) ;
	 9834    }
	 9835 }


...which relies on heavy lifting by THD_3dmm_to_3dind() in thd_coords.c :

	146 THD_ivec3 THD_3dmm_to_3dind( THD_3dim_dataset *dset , THD_fvec3 fv )
	147 {
	148    THD_dataxes *daxes ;
	149    THD_ivec3    iv ;
	150 
	151    daxes = CURRENT_DAXES(dset) ;
	152 
	153    iv.ijk[0] = (fv.xyz[0] - daxes->xxorg) / daxes->xxdel + 0.499 ;
	154    iv.ijk[1] = (fv.xyz[1] - daxes->yyorg) / daxes->yydel + 0.499 ;
	155    iv.ijk[2] = (fv.xyz[2] - daxes->zzorg) / daxes->zzdel + 0.499 ;
	156 
	157         if( iv.ijk[0] < 0            ) iv.ijk[0] = 0 ;
	158    else if( iv.ijk[0] > daxes->nxx-1 ) iv.ijk[0] = daxes->nxx-1 ;
	159 
	160         if( iv.ijk[1] < 0            ) iv.ijk[1] = 0 ;
	161    else if( iv.ijk[1] > daxes->nyy-1 ) iv.ijk[1] = daxes->nyy-1 ;
	162 
	163         if( iv.ijk[2] < 0            ) iv.ijk[2] = 0 ;
	164    else if( iv.ijk[2] > daxes->nzz-1 ) iv.ijk[2] = daxes->nzz-1 ;
	165 
	166    return iv ;
	167 }