source: issm/trunk/src/m/model/slope.m@ 9725

function [sx,sy,s]=slope(md)
%SLOPE - compute the surface slope
%
%   Usage:
%      [sx,sy,s]=slope(md)

%load some variables (it is much faster if the variab;es are loaded from md once for all) 
if (md.mesh.dimension==2),
        numberofelements=md.mesh.numberofelements;
        numberofnodes=md.mesh.numberofvertices;
        index=md.elements;
        x=md.x; y=md.y;
else
        numberofelements=md.mesh.numberofelements2d;
        numberofnodes=md.mesh.numberofvertices2d;
        index=md.elements2d;
        x=md.x2d; y=md.y2d;
end

%compute nodal functions coefficients N(x,y)=alpha x + beta y + gamma
[alpha beta]=GetNodalFunctionsCoeff(index,x,y);

summation=[1;1;1];
sx=(md.geometry.surface(index).*alpha)*summation;
sy=(md.geometry.surface(index).*beta)*summation;
s=sqrt(sx.^2+sy.^2);

if md.mesh.dimension==3,
        sx=project3d(md,sx,'element');
        sy=project3d(md,sy,'element');
        s=sqrt(sx.^2+sy.^2);
end