geom3d(2)

NAME
geom3d - projection from 3D on 2D

CALLING SEQUENCE
[x,y]=geom3d(x1,y1,z1)

PARAMETERS

x1,y1,z1
    : real matrices of the same size (points in R3)

x,y : real matrices of the same size as x1,y1 or z1

DESCRIPTION
After having used a 3d plotting function as plot3d, plot3d1 and param3d, this function gives the correspondence between a point in R3 space (x1(i),y1(i),z1(i)) and the corresponding point in the projected graphic plan (x(i),y(j)). all the graphical primitives working on (x,y) can then be used for superposition on a plot3d

EXAMPLE
deff("[z]=surf(x,y)","z=sin(x)*cos(y)");
t=%pi*(-10:10)/10;
fplot3d(t,t,surf,35,45,"X@Y@Z");
    //Gives a plot3d
    //now  (t,t,sin(t).*cos(t) ) is a curve on the surface
    //which can be drawn using param3d or the following code
[x,y]=geom3d(t,t,sin(t).*cos(t));
xpoly(x,y,"lines")
    //adding a comment
[x,y]=geom3d([0,0],[0,0],[5,0]);
xsegs(x,y);
xstring(x(1),y(1)," The point (0,0,0)");

AUTHOR
J.Ph.C.