[MBsysPy][cross] np.array[True] is not the same as np.array[1]

MBsysC/mbs_interface/MBsysPy/mbs_algebra.py

@@ -211,12 +211,12 @@ def cross_product(v1, v2, vres=None, index_1=True):
         vres = np.zeros(3 + index_1)
     # For faster reading, terms are aligned.
     # For comprenhension:
-    # index_1 alone is index [1]
+    # index_1 + 0 is index [1], index_1 alone does not work as index_1 is True/False
     # index_1 + 1   is index [2]
     # index_1 + 2   is index [3]
-    vres[index_1    ] = v1[index_1 + 1] * v2[index_1 + 2] - v1[index_1 + 2] * v2[index_1 + 1]
-    vres[index_1 + 1] = v1[index_1 + 2] * v2[index_1    ] - v1[index_1    ] * v2[index_1 + 2]
-    vres[index_1 + 2] = v1[index_1    ] * v2[index_1 + 1] - v1[index_1 + 1] * v2[index_1    ]
+    vres[index_1 + 0] = v1[index_1 + 1] * v2[index_1 + 2] - v1[index_1 + 2] * v2[index_1 + 1]
+    vres[index_1 + 1] = v1[index_1 + 2] * v2[index_1 + 0] - v1[index_1 + 0] * v2[index_1 + 2]
+    vres[index_1 + 2] = v1[index_1 + 0] * v2[index_1 + 1] - v1[index_1 + 1] * v2[index_1 + 0]
     # And the previous formulaes are the cross product of 2 vector of 3 elements, first element being in index [1].
 
     return vres