138 lines
4.4 KiB
C++
138 lines
4.4 KiB
C++
/// @ref gtx_fast_exponential
|
|
/// @file glm/gtx/fast_exponential.inl
|
|
|
|
namespace glm
|
|
{
|
|
// fastPow:
|
|
template <typename genType>
|
|
GLM_FUNC_QUALIFIER genType fastPow(genType x, genType y)
|
|
{
|
|
return exp(y * log(x));
|
|
}
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastPow(vecType<T, P> const & x, vecType<T, P> const & y)
|
|
{
|
|
return exp(y * log(x));
|
|
}
|
|
|
|
template <typename T>
|
|
GLM_FUNC_QUALIFIER T fastPow(T x, int y)
|
|
{
|
|
T f = static_cast<T>(1);
|
|
for(int i = 0; i < y; ++i)
|
|
f *= x;
|
|
return f;
|
|
}
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastPow(vecType<T, P> const & x, vecType<int, P> const & y)
|
|
{
|
|
vecType<T, P> Result(uninitialize);
|
|
for(length_t i = 0, n = x.length(); i < n; ++i)
|
|
Result[i] = fastPow(x[i], y[i]);
|
|
return Result;
|
|
}
|
|
|
|
// fastExp
|
|
// Note: This function provides accurate results only for value between -1 and 1, else avoid it.
|
|
template <typename T>
|
|
GLM_FUNC_QUALIFIER T fastExp(T x)
|
|
{
|
|
// This has a better looking and same performance in release mode than the following code. However, in debug mode it's slower.
|
|
// return 1.0f + x * (1.0f + x * 0.5f * (1.0f + x * 0.3333333333f * (1.0f + x * 0.25 * (1.0f + x * 0.2f))));
|
|
T x2 = x * x;
|
|
T x3 = x2 * x;
|
|
T x4 = x3 * x;
|
|
T x5 = x4 * x;
|
|
return T(1) + x + (x2 * T(0.5)) + (x3 * T(0.1666666667)) + (x4 * T(0.041666667)) + (x5 * T(0.008333333333));
|
|
}
|
|
/* // Try to handle all values of float... but often shower than std::exp, glm::floor and the loop kill the performance
|
|
GLM_FUNC_QUALIFIER float fastExp(float x)
|
|
{
|
|
const float e = 2.718281828f;
|
|
const float IntegerPart = floor(x);
|
|
const float FloatPart = x - IntegerPart;
|
|
float z = 1.f;
|
|
|
|
for(int i = 0; i < int(IntegerPart); ++i)
|
|
z *= e;
|
|
|
|
const float x2 = FloatPart * FloatPart;
|
|
const float x3 = x2 * FloatPart;
|
|
const float x4 = x3 * FloatPart;
|
|
const float x5 = x4 * FloatPart;
|
|
return z * (1.0f + FloatPart + (x2 * 0.5f) + (x3 * 0.1666666667f) + (x4 * 0.041666667f) + (x5 * 0.008333333333f));
|
|
}
|
|
|
|
// Increase accuracy on number bigger that 1 and smaller than -1 but it's not enough for high and negative numbers
|
|
GLM_FUNC_QUALIFIER float fastExp(float x)
|
|
{
|
|
// This has a better looking and same performance in release mode than the following code. However, in debug mode it's slower.
|
|
// return 1.0f + x * (1.0f + x * 0.5f * (1.0f + x * 0.3333333333f * (1.0f + x * 0.25 * (1.0f + x * 0.2f))));
|
|
float x2 = x * x;
|
|
float x3 = x2 * x;
|
|
float x4 = x3 * x;
|
|
float x5 = x4 * x;
|
|
float x6 = x5 * x;
|
|
float x7 = x6 * x;
|
|
float x8 = x7 * x;
|
|
return 1.0f + x + (x2 * 0.5f) + (x3 * 0.1666666667f) + (x4 * 0.041666667f) + (x5 * 0.008333333333f)+ (x6 * 0.00138888888888f) + (x7 * 0.000198412698f) + (x8 * 0.0000248015873f);;
|
|
}
|
|
*/
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastExp(vecType<T, P> const & x)
|
|
{
|
|
return detail::functor1<T, T, P, vecType>::call(fastExp, x);
|
|
}
|
|
|
|
// fastLog
|
|
template <typename genType>
|
|
GLM_FUNC_QUALIFIER genType fastLog(genType x)
|
|
{
|
|
return std::log(x);
|
|
}
|
|
|
|
/* Slower than the VC7.1 function...
|
|
GLM_FUNC_QUALIFIER float fastLog(float x)
|
|
{
|
|
float y1 = (x - 1.0f) / (x + 1.0f);
|
|
float y2 = y1 * y1;
|
|
return 2.0f * y1 * (1.0f + y2 * (0.3333333333f + y2 * (0.2f + y2 * 0.1428571429f)));
|
|
}
|
|
*/
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastLog(vecType<T, P> const & x)
|
|
{
|
|
return detail::functor1<T, T, P, vecType>::call(fastLog, x);
|
|
}
|
|
|
|
//fastExp2, ln2 = 0.69314718055994530941723212145818f
|
|
template <typename genType>
|
|
GLM_FUNC_QUALIFIER genType fastExp2(genType x)
|
|
{
|
|
return fastExp(0.69314718055994530941723212145818f * x);
|
|
}
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastExp2(vecType<T, P> const & x)
|
|
{
|
|
return detail::functor1<T, T, P, vecType>::call(fastExp2, x);
|
|
}
|
|
|
|
// fastLog2, ln2 = 0.69314718055994530941723212145818f
|
|
template <typename genType>
|
|
GLM_FUNC_QUALIFIER genType fastLog2(genType x)
|
|
{
|
|
return fastLog(x) / 0.69314718055994530941723212145818f;
|
|
}
|
|
|
|
template <typename T, precision P, template <typename, precision> class vecType>
|
|
GLM_FUNC_QUALIFIER vecType<T, P> fastLog2(vecType<T, P> const & x)
|
|
{
|
|
return detail::functor1<T, T, P, vecType>::call(fastLog2, x);
|
|
}
|
|
}//namespace glm
|