[FEAT] Matrix : add minor

raytracing/src/matrix.cpp

@@ -226,6 +226,13 @@ Matrix Matrix::sub_matrix(uint8_t a_rows, uint8_t a_cols)
 
 /* ------------------------------------------------------------------------- */
 
+double Matrix::minor(uint8_t a_rows, uint8_t a_cols)
+{
+    return sub_matrix(a_rows, a_cols).determinant();
+}
+
+/* ------------------------------------------------------------------------- */
+
 Matrix Matrix::identity(void)
 {
     Matrix the_identity = {

raytracing/src/matrix.h

@@ -62,6 +62,7 @@ namespace Raytracer
         bool transpose(void);
         double determinant(void);
         Matrix sub_matrix(uint8_t a_rows, uint8_t a_cols);
+        double minor(uint8_t a_rows, uint8_t a_cols);
 
         static Matrix identity(void);
 

tests/03_matrix.cpp

@@ -277,3 +277,20 @@ TEST_CASE("[Matrix] A submatrix of a 4x4 matrix is a 3x3 matrix", "[Matrix]")
 
     REQUIRE(a.sub_matrix(2, 1) == b);
 }
+
+/* ------------------------------------------------------------------------- */
+
+TEST_CASE("[Matrix] Calculating a minor of a 3x3 matrix", "[Matrix]")
+{
+    Matrix a = {
+        {3,  5,  0},
+        {2, -1, -7},
+        {6, -1,  5}
+    };
+
+    Matrix b = a.sub_matrix(1, 0);
+
+    REQUIRE(b.determinant() == 25);
+
+    REQUIRE(a.minor(1, 0) == 25);
+}