Issue #56:

Changed initialization of direction matrix

products/+elltool/+doc/+snip/s_chapter06_section07_snippet06.m

@@ -6,13 +6,15 @@
 % initialize direction matrix
 nDims = 4;
 nDirs = 1;
-dirMeshVec = 0 : (2 * pi / nDirs) : 2 * pi;
-dirNum = length(dirMeshVec) ^ nDims;
-[a1, a2, a3, a4] = ndgrid(dirMeshVec, dirMeshVec, dirMeshVec, dirMeshVec);
-lineDir1Mat = reshape(a1, [1, dirNum]);
-lineDir2Mat = reshape(a2, [1, dirNum]);
-lineDir3Mat = reshape(a3, [1, dirNum]);
-lineDir4Mat = reshape(a4, [1, dirNum]);
+psi = 0 : (pi / nDirs) : pi;
+theta = 0 : (pi / nDirs) : pi;
+phi = 0 : (2 * pi / nDirs) : 2 * pi;
+dirNum = length(psi) ^ (nDims - 1);
+[a1, a2, a3] = ndgrid(psi, theta, phi);
+lineDir1Mat = reshape(cos(a1), [1, dirNum]);
+lineDir2Mat = reshape(sin(a1) .* cos(a2), [1, dirNum]);
+lineDir3Mat = reshape(sin(a1) .* sin(a2) .* cos(a3), [1, dirNum]);
+lineDir4Mat = reshape(sin(a1) .* sin(a2) .* sin(a3), [1, dirNum]);
 dirMat = [lineDir1Mat; lineDir2Mat; lineDir3Mat; lineDir4Mat];
 dirMat = dirMat(:, 2 : end);
 dirMat = dirMat ./ sqrt(repmat(sum(dirMat .^ 2, 1), nDims, 1));