section g of routines in pl3d.i

functions in pl3d.i - g

get3_centroid


    get3_centroid(xyz, nxyz)  
 or get3_centroid(xyz)  


return 3D centroids for polygons with vertices XYZ.  If NXYZ is  
specified, XYZ should be 3-by-sum(nxyz), with NXYZ being the  
list of numbers of vertices for each polygon (as for the plfp  
function).  If NXYZ is not specified, XYZ should be a quadrilateral  
mesh, 3-by-ni-by-nj (as for the plf function).  In the first case,  
the return value is 3-by-numberof(NXYZ); in the second case, the  
return value is 3-by-(ni-1)-by-(nj-1).  
The centroids are constructed as the mean value of all vertices  
of each polygon.  
Interpreted function, defined at i/pl3d.i   line 480

SEE ALSO: get3_normal, get3_light

get3_light


    get3_light(xyz, nxyz)  
 or get3_light(xyz)  


return 3D lighting for polygons with vertices XYZ.  If NXYZ is  
specified, XYZ should be 3-by-sum(nxyz), with NXYZ being the  
list of numbers of vertices for each polygon (as for the plfp  
function).  If NXYZ is not specified, XYZ should be a quadrilateral  
mesh, 3-by-ni-by-nj (as for the plf function).  In the first case,  
the return value is numberof(NXYZ); in the second case, the  
return value is (ni-1)-by-(nj-1).  
The parameters of the lighting calculation are set by the  
light3 function.  
Interpreted function, defined at i/pl3d.i   line 363

SEE ALSO: light3, set3_object, get3_normal, get3_centroid

get3_normal


    get3_normal(xyz, nxyz)  
 or get3_normal(xyz)  


return 3D normals for polygons with vertices XYZ.  If NXYZ is  
specified, XYZ should be 3-by-sum(nxyz), with NXYZ being the  
list of numbers of vertices for each polygon (as for the plfp  
function).  If NXYZ is not specified, XYZ should be a quadrilateral  
mesh, 3-by-ni-by-nj (as for the plf function).  In the first case,  
the return value is 3-by-numberof(NXYZ); in the second case, the  
return value is 3-by-(ni-1)-by-(nj-1).  
The normals are constructed from the cross product of the lines  
joining the midpoints of two edges which as nearly quarter the  
polygon as possible (the medians for a quadrilateral).  No check  
is made that these not be parallel; the returned "normal" is  
[0,0,0] in that case.  Also, if the polygon vertices are not  
coplanar, the "normal" has no precisely definable meaning.  
Interpreted function, defined at i/pl3d.i   line 421

SEE ALSO: get3_centroid, get3_light

get3_xy


    get3_xy, xyz, x, y  
 or get3_xy, xyz, x, y, z, 1  


Given 3-by-anything coordinates XYZ, return X and Y in viewer's  
coordinate system (set by rot3, mov3, orient3, etc.).  If the  
fifth argument is present and non-zero, also return Z (for use  
in sort3d or get3_light, for example).  If the camera position  
has been set to a finite distance with setz3, the returned  
coordinates will be tangents of angles for a perspective  
drawing (and Z will be scaled by 1/zc).  
Interpreted function, defined at i/pl3d.i   line 520

SEE ALSO: sort3d, get3_light, rot3, setz3, set3_object

gnomon


    gnomon  
 or gnomon, onoff  


Toggle the gnomon display.  If ONOFF is non-nil and non-zero,  
turn on the gnomon.  If ONOFF is zero, turn off the gnomon.  
The gnomon shows the X, Y, and Z axis directions in the  
object coordinate system.  The directions are labeled.  
The gnomon is always infinitely far behind the object  
(away from the camera).  
There is a mirror-through-the-screen-plane ambiguity in the  
display which is resolved in two ways: (1) The (X,Y,Z)  
coordinate system is right-handed, and (2) If the tip of an  
axis projects into the screen, it's label is drawn in opposite  
polarity to the other text on the screen.  
Interpreted function, defined at i/pl3d.i   line 734