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LibGfx: Make Matrix class consistently row-major

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Matrix elements were interpreted in different ways.
This makes it definitely row-major, allowing initialization via
initializer list in a standard scientific order. Also matrix
multiplication now happens in the correct order and accessing
elements happens as m_elements[row][column].
This commit is contained in:
Stephan Unverwerth 2021-05-13 19:59:57 +02:00 • committed by Andreas Kling
parent a5194274af
commit 0833db0874
4 changed files with 49 additions and 31 deletions
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22
Userland/Libraries/LibGfx/Matrix.h
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@ -49,23 +49,23 @@ public:
auto& element = product.m_elements[i][j];
if constexpr (N == 4) {
element = m_elements[0][j] * other.m_elements[i][0]
+ m_elements[1][j] * other.m_elements[i][1]
+ m_elements[2][j] * other.m_elements[i][2]
+ m_elements[3][j] * other.m_elements[i][3];
element = m_elements[i][0] * other.m_elements[0][j]
+ m_elements[i][1] * other.m_elements[1][j]
+ m_elements[i][2] * other.m_elements[2][j]
+ m_elements[i][3] * other.m_elements[3][j];
} else if constexpr (N == 3) {
element = m_elements[0][j] * other.m_elements[i][0]
+ m_elements[1][j] * other.m_elements[i][1]
+ m_elements[2][j] * other.m_elements[i][2];
element = m_elements[i][0] * other.m_elements[0][j]
+ m_elements[i][1] * other.m_elements[1][j]
+ m_elements[i][2] * other.m_elements[2][j];
} else if constexpr (N == 2) {
element = m_elements[0][j] * other.m_elements[i][0]
+ m_elements[1][j] * other.m_elements[i][1];
element = m_elements[i][0] * other.m_elements[0][j]
+ m_elements[i][1] * other.m_elements[1][j];
} else if constexpr (N == 1) {
element = m_elements[0][j] * other.m_elements[i][0];
element = m_elements[i][0] * other.m_elements[0][j];
} else {
T value {};
for (size_t k = 0; k < N; ++k)
value += m_elements[k][j] * other.m_elements[i][k];
value += m_elements[i][k] * other.m_elements[k][j];
element = value;
}