gtMathsCross: added other possible directions for cross product

Signed-off-by: Nicola Vigano <nicola.vigano@esrf.fr>

zUtil_Maths/gtMathsCross.m

-function res = gtMathsCross(vec1, vec2)
+function res = gtMathsCross(vec1, vec2, dim)
 % FUNCTION res = gtMathsCross(vec1, vec2)
 % 
 %   Computes the cross product of vectors 1 and 2.
@@ -8,7 +8,21 @@ function res = gtMathsCross(vec1, vec2)
 %   Can be 1 order of magnitude faster than MATLAB's cross built-in function.
 %
 
-    res = [ vec1(:, 2) .* vec2(:, 3) - vec1(:, 3) .* vec2(:, 2), ...
-            vec1(:, 3) .* vec2(:, 1) - vec1(:, 1) .* vec2(:, 3), ...
-            vec1(:, 1) .* vec2(:, 2) - vec1(:, 2) .* vec2(:, 1) ];
+    if (~exist('dim', 'var') || isempty(dim))
+        dim = 2;
+    end
+    switch (dim)
+        case 1
+            res = [ vec1(2, :, :) .* vec2(3, :, :) - vec1(3, :, :) .* vec2(2, :, :), ...
+                    vec1(3, :, :) .* vec2(1, :, :) - vec1(1, :, :) .* vec2(3, :, :), ...
+                    vec1(1, :, :) .* vec2(2, :, :) - vec1(2, :, :) .* vec2(1, :, :) ];
+        case 2
+            res = [ vec1(:, 2, :) .* vec2(:, 3, :) - vec1(:, 3, :) .* vec2(:, 2, :), ...
+                    vec1(:, 3, :) .* vec2(:, 1, :) - vec1(:, 1, :) .* vec2(:, 3, :), ...
+                    vec1(:, 1, :) .* vec2(:, 2, :) - vec1(:, 2, :) .* vec2(:, 1, :) ];
+        case 3
+            res = [ vec1(:, :, 2) .* vec2(:, :, 3) - vec1(:, :, 3) .* vec2(:, :, 2), ...
+                    vec1(:, :, 3) .* vec2(:, :, 1) - vec1(:, :, 1) .* vec2(:, :, 3), ...
+                    vec1(:, :, 1) .* vec2(:, :, 2) - vec1(:, :, 2) .* vec2(:, :, 1) ];
+    end
 end