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Add explanation to matrix multiplication

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Brendan Zabarauskas 2012-11-07 11:07:13 +10:00
parent 1fe0d52fe4
commit bfe318aff5
1 changed files with 3 additions and 0 deletions
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3
src/matrix.rs
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@ -698,6 +698,9 @@ pub impl<T:Copy Num NumCast FuzzyEq> Mat4<T>: SquareMatrix<T> {
#[inline(always)] #[inline(always)]
pure fn mul_m(other: &Mat4<T>) -> Mat4<T> { pure fn mul_m(other: &Mat4<T>) -> Mat4<T> {
// Surprisingly when building with optimisation turned on this is actually
// faster than writing out the matrix multiplication in expanded form.
// If you don't believe me, see ./test/performance/matrix_mul.rs
Mat4::new(self.row(0).dot(&other.col(0)), self.row(1).dot(&other.col(0)), self.row(2).dot(&other.col(0)), self.row(3).dot(&other.col(0)), Mat4::new(self.row(0).dot(&other.col(0)), self.row(1).dot(&other.col(0)), self.row(2).dot(&other.col(0)), self.row(3).dot(&other.col(0)),
self.row(0).dot(&other.col(1)), self.row(1).dot(&other.col(1)), self.row(2).dot(&other.col(1)), self.row(3).dot(&other.col(1)), self.row(0).dot(&other.col(1)), self.row(1).dot(&other.col(1)), self.row(2).dot(&other.col(1)), self.row(3).dot(&other.col(1)),
self.row(0).dot(&other.col(2)), self.row(1).dot(&other.col(2)), self.row(2).dot(&other.col(2)), self.row(3).dot(&other.col(2)), self.row(0).dot(&other.col(2)), self.row(1).dot(&other.col(2)), self.row(2).dot(&other.col(2)), self.row(3).dot(&other.col(2)),