lecture5-6

Sign23 count sumallsamesign end function z getzcross

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Unformatted text preview: gles.txt % which contain the origin %load triangles.txt; %filename = input('name of triangles file: ','s'); triangles = load(filename); [rows cols] = size(triangles) a = triangles(:, 1:2); b = triangles(:, 3:4); c = triangles(:, 5:6); count = originInTriangle(a,b,c); fprintf('There are %5.0f triangles that enclose 0,0\n',count); end function count = originInTriangle( a,b,c ) %Checks to see if point p is contained in triangle a,b,c % a,b,c in xy plane z1 = getZcross(a,b); z2 = getZcross(b,c); z3 = getZcross(c,a); sign12 = sign(z1).*(sign(z1) == sign(z2)); sign23 = sign(z2).*(sign(z2) == sign(z3)); allSameSign = sign12.*sign23; count = sum(allSameSign); end function [ z ] = getZcross( a,b ) %getZcross returns the z-component of the cross product of % the vector a to b and b to 0,0 [m n] = size(a); zerocol = zeros(m,1); r = [b(:,1)-a(:,1) b(:,2)-a(:,2) zerocol]; s = [0 - b(:,1), 0 - b(:,2) zerocol]; v = crossProduct(r,s); z = v(:,3); end function [ xc ] = crossProduct( a,b ) %crossProduct returns the cross product components of a x b [m n] = size(a); xc = zeros(m,3); ax = a(:,1);...
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