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polynomial: remove some useless maths operations

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This commit is contained in:
Danny Robson 2015-01-22 00:27:10 +11:00
parent aca28a65e5
commit 13188ca83c
1 changed files with 8 additions and 8 deletions
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16
polynomial.cpp
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@ -68,12 +68,12 @@ namespace util { namespace polynomial {
namespace util { namespace polynomial { namespace util { namespace polynomial {
template <> template <>
std::array<float,3> std::array<float,3>
solve (std::array<float,4> coeff) solve (std::array<float,4> coeffs)
{ {
const float _a = coeff[0]; const float _a = coeffs[0];
const float _b = coeff[1]; const float _b = coeffs[1];
const float _c = coeff[2]; const float _c = coeffs[2];
const float _d = coeff[3]; const float _d = coeffs[3];
if (almost_zero (_a)) { if (almost_zero (_a)) {
auto s = solve<3> ({_b, _c, _d}); auto s = solve<3> ({_b, _c, _d});
@ -92,8 +92,8 @@ namespace util { namespace polynomial {
const float c = _d / _a; const float c = _d / _a;
// Substituate x = y - a / 3 to eliminate the quadric. Now: x^3 + px + q = 0 // Substituate x = y - a / 3 to eliminate the quadric. Now: x^3 + px + q = 0
float p = (-1 / 3.f * a * a + b) / 3.f; float p = (-a * a / 3.f + b) / 3.f;
float q = (2 / 27.f * a * a * a - 1 / 3.f * a * b + c) / 2.f; float q = (2 * a * a * a / 27.f - a * b /3.f + c) / 2.f;
// Solve using Cardano's method // Solve using Cardano's method
float D = q * q + p * p * p; float D = q * q + p * p * p;
@ -108,7 +108,7 @@ namespace util { namespace polynomial {
s[1] = -u; s[1] = -u;
} }
} else if (D < 0) { } else if (D < 0) {
float phi = 1 / 3.f * std::acos (-q / std::sqrt (-p * p * p)); float phi = std::acos (-q / std::sqrt (-p * p * p)) / 3.f;
float t = 2 * std::sqrt (-p); float t = 2 * std::sqrt (-p);
s[0] = t * std::cos (phi); s[0] = t * std::cos (phi);