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[FEAT] Matrix: Add cofactor

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NADAL Jean-Baptiste
2024-02-02 18:17:27 +01:00
parent f2a7ce738e
commit 47400a4d14
3 changed files with 38 additions and 7 deletions
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24
raytracing/src/matrix.cpp
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@@ -208,16 +208,16 @@ double Matrix::determinant(void)
/* ------------------------------------------------------------------------- */ /* ------------------------------------------------------------------------- */
Matrix Matrix::sub_matrix(uint8_t a_rows, uint8_t a_cols) Matrix Matrix::sub_matrix(uint8_t a_row, uint8_t a_col)
{ {
Matrix the_sub = *this; Matrix the_sub = *this;
the_sub.m_data.erase(the_sub.m_data.begin() + a_rows); the_sub.m_data.erase(the_sub.m_data.begin() + a_row);
the_sub.m_rows--; the_sub.m_rows--;
for (int the_row = 0; the_row < the_sub.m_rows; the_row++) for (int the_row = 0; the_row < the_sub.m_rows; the_row++)
{ {
the_sub.m_data[the_row].erase(the_sub.m_data[the_row].begin() + a_cols); the_sub.m_data[the_row].erase(the_sub.m_data[the_row].begin() + a_col);
} }
the_sub.m_cols--; the_sub.m_cols--;
@@ -226,9 +226,23 @@ Matrix Matrix::sub_matrix(uint8_t a_rows, uint8_t a_cols)
/* ------------------------------------------------------------------------- */ /* ------------------------------------------------------------------------- */
double Matrix::minor(uint8_t a_rows, uint8_t a_cols) double Matrix::minor(uint8_t a_row, uint8_t a_col)
{ {
return sub_matrix(a_rows, a_cols).determinant(); return sub_matrix(a_row, a_col).determinant();
}
/* ------------------------------------------------------------------------- */
double Matrix::cofactor(uint8_t a_row, uint8_t a_col)
{
int8_t an_inverter = 1;
if ((a_row + a_col) % 2 != 0)
{
an_inverter = -1;
}
return an_inverter * minor(a_row, a_col);
} }
/* ------------------------------------------------------------------------- */ /* ------------------------------------------------------------------------- */

5
raytracing/src/matrix.h
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@@ -61,8 +61,9 @@ namespace Raytracer
bool transpose(void); bool transpose(void);
double determinant(void); double determinant(void);
Matrix sub_matrix(uint8_t a_rows, uint8_t a_cols); Matrix sub_matrix(uint8_t a_row, uint8_t a_col);
double minor(uint8_t a_rows, uint8_t a_cols); double minor(uint8_t a_row, uint8_t a_col);
double cofactor(uint8_t a_row, uint8_t a_col);
static Matrix identity(void); static Matrix identity(void);

16
tests/03_matrix.cpp
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@@ -294,3 +294,19 @@ TEST_CASE("[Matrix] Calculating a minor of a 3x3 matrix", "[Matrix]")
REQUIRE(a.minor(1, 0) == 25); REQUIRE(a.minor(1, 0) == 25);
} }
/* ------------------------------------------------------------------------- */
TEST_CASE("[Matrix] Calculating a cofactor of a 3x3 matrix", "[Matrix]")
{
Matrix a = {
{3, 5, 0},
{2, -1, -7},
{6, -1, 5}
};
REQUIRE(a.minor(0, 0) == -12.0);
REQUIRE(a.cofactor(0, 0) == -12.0);
REQUIRE(a.minor(1, 0) == 25.0);
REQUIRE(a.cofactor(1, 0) == -25.0);
}