ptarray_calc_areas()

void ptarray_calc_areas	(	EFFECTIVE_AREAS *	ea,
		int	avoid_collaps,
		int	set_area,
		double	trshld
	)

We calculate the effective area for the first time.

Definition at line 349 of file effectivearea.c.

References areanode::area, area(), POINTARRAY::flags, FLAGS_GET_Z, getPoint_internal(), EFFECTIVE_AREAS::initial_arealist, EFFECTIVE_AREAS::inpts, LWDEBUG, LWDEBUGF, areanode::next, POINTARRAY::npoints, areanode::prev, EFFECTIVE_AREAS::res_arealist, return(), triarea2d(), triarea3d(), and tune_areas().

Referenced by do_test_lwgeom_effectivearea(), and ptarray_set_effective_area().

{
        LWDEBUG(2, "Entered  ptarray_calc_areas");
        int i;
        int npoints=ea->inpts->npoints;
        int is3d = FLAGS_GET_Z(ea->inpts->flags);
        double area;

        const double *P1;
        const double *P2;
        const double *P3;

        P1 = (double*)getPoint_internal(ea->inpts, 0);
        P2 = (double*)getPoint_internal(ea->inpts, 1);

        /*The first and last point shall always have the maximum effective area. We use float max to not make trouble for bbox*/
        ea->initial_arealist[0].area=ea->initial_arealist[npoints-1].area=FLT_MAX;
        ea->res_arealist[0]=ea->res_arealist[npoints-1]=FLT_MAX;

        ea->initial_arealist[0].next=1;
        ea->initial_arealist[0].prev=0;

        for (i=1;i<(npoints)-1;i++)
        {
                ea->initial_arealist[i].next=i+1;
                ea->initial_arealist[i].prev=i-1;
                P3 = (double*)getPoint_internal(ea->inpts, i+1);

                if(is3d)
                        area=triarea3d(P1, P2, P3);
                else
                        area=triarea2d(P1, P2, P3);

                LWDEBUGF(4,"Write area %lf to point %d on address %p",area,i,&(ea->initial_arealist[i].area));
                ea->initial_arealist[i].area=area;
                P1=P2;
                P2=P3;

        }
                ea->initial_arealist[npoints-1].next=npoints-1;
                ea->initial_arealist[npoints-1].prev=npoints-2;

        for (i=1;i<(npoints)-1;i++)
        {
                ea->res_arealist[i]=FLT_MAX;
        }

        tune_areas(ea,avoid_collaps,set_area, trshld);
        return ;
}

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