/* Routine to draw a grid around the back side of the 3d plot */
/* wih hidden line removal */

#include "plplot.h"
#include <math.h>

void plgrid3(tick)
float tick;
{
    float xmin, ymin, zmin, xmax, ymax, zmax, zscale;
    float cxx, cxy, cyx, cyy, cyz;
    int u[3], v[3];
    int nsub, mode, prec;
    float tp;

    gw3wc(&cxx,&cxy,&cyx,&cyy,&cyz);
    gdom(&xmin,&xmax,&ymin,&ymax);
    grange(&zscale,&zmin,&zmax);

    nsub = 0;
    pldtik(zmin,zmax,&tick,&nsub,&mode,&prec);
    tp = tick * floor(zmin/tick) + tick;

    if (cxx >= 0.0 && cxy <= 0.0)  {
        while ( tp <= zmax ) {
            u[0] = wcpcx(w3wcx(xmin,ymax,tp));
            v[0] = wcpcy(w3wcy(xmin,ymax,tp));
            u[1] = wcpcx(w3wcx(xmax,ymax,tp));
            v[1] = wcpcy(w3wcy(xmax,ymax,tp));
            u[2] = wcpcx(w3wcx(xmax,ymin,tp));
            v[2] = wcpcy(w3wcy(xmax,ymin,tp));
            plnxtv(u,v,3,2);

            tp += tick;
        }
        u[0] = wcpcx(w3wcx(xmax,ymax,zmin));
        v[0] = wcpcy(w3wcy(xmax,ymax,zmin));
        u[1] = wcpcx(w3wcx(xmax,ymax,zmax));
        v[1] = wcpcy(w3wcy(xmax,ymax,zmax));
        plnxtv(u,v,2,2);
    }
    else if(cxx <= 0.0  && cxy <= 0.0)  {
        while ( tp <= zmax ) {
            u[0] = wcpcx(w3wcx(xmax,ymax,tp));
            v[0] = wcpcy(w3wcy(xmax,ymax,tp));
            u[1] = wcpcx(w3wcx(xmax,ymin,tp));
            v[1] = wcpcy(w3wcy(xmax,ymin,tp));
            u[2] = wcpcx(w3wcx(xmin,ymin,tp));
            v[2] = wcpcy(w3wcy(xmin,ymin,tp));
            plnxtv(u,v,3,2);

            tp += tick;
        }
        u[0] = wcpcx(w3wcx(xmax,ymin,zmin));
        v[0] = wcpcy(w3wcy(xmax,ymin,zmin));
        u[1] = wcpcx(w3wcx(xmax,ymin,zmax));
        v[1] = wcpcy(w3wcy(xmax,ymin,zmax));
        plnxtv(u,v,2,2);
    }
    else if(cxx <= 0.0  && cxy >= 0.0)  {
        while ( tp <= zmax ) {
            u[0] = wcpcx(w3wcx(xmax,ymin,tp));
            v[0] = wcpcy(w3wcy(xmax,ymin,tp));
            u[1] = wcpcx(w3wcx(xmin,ymin,tp));
            v[1] = wcpcy(w3wcy(xmin,ymin,tp));
            u[2] = wcpcx(w3wcx(xmin,ymax,tp));
            v[2] = wcpcy(w3wcy(xmin,ymax,tp));
            plnxtv(u,v,3,2);

            tp += tick;
        }
        u[0] = wcpcx(w3wcx(xmin,ymin,zmin));
        v[0] = wcpcy(w3wcy(xmin,ymin,zmin));
        u[1] = wcpcx(w3wcx(xmin,ymin,zmax));
        v[1] = wcpcy(w3wcy(xmin,ymin,zmax));
        plnxtv(u,v,2,2);
    }
    else if(cxx >= 0.0  && cxy >= 0.0)  {
        while ( tp <= zmax ) {
            u[0] = wcpcx(w3wcx(xmin,ymin,tp));
            v[0] = wcpcy(w3wcy(xmin,ymin,tp));
            u[1] = wcpcx(w3wcx(xmin,ymax,tp));
            v[1] = wcpcy(w3wcy(xmin,ymax,tp));
            u[2] = wcpcx(w3wcx(xmax,ymax,tp));
            v[2] = wcpcy(w3wcy(xmax,ymax,tp));
            plnxtv(u,v,3,2);

            tp += tick;
        }
        u[0] = wcpcx(w3wcx(xmin,ymax,zmin));
        v[0] = wcpcy(w3wcy(xmin,ymax,zmin));
        u[1] = wcpcx(w3wcx(xmin,ymax,zmax));
        v[1] = wcpcy(w3wcy(xmin,ymax,zmax));
        plnxtv(u,v,2,2);
    }
}