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Factorized fastInversesqrt code

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This commit is contained in:
Christophe Riccio 2013-09-15 14:39:59 +02:00
parent eeacdf37a0
commit 6838815f9f
3 changed files with 21 additions and 38 deletions
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2
glm/core/func_exponential.hpp
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@ -104,7 +104,7 @@ namespace glm
/// @see <a href="http://www.opengl.org/registry/doc/GLSLangSpec.4.20.8.pdf">GLSL 4.20.8 specification, section 8.2 Exponential Functions</a>
template <typename genType>
GLM_FUNC_DECL genType sqrt(genType const & x);
/// Returns the reciprocal of the positive square root of x.
///
/// @param x inversesqrt function is defined for input values of x defined in the range [0, inf+) in the limit of the type precision.

47
glm/core/func_exponential.inl
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@ -153,52 +153,43 @@ namespace _detail
VECTORIZE_VEC(inversesqrt)
namespace detail
{
template <typename genType, typename genUType>
genType fastInversesqrt(genType const & v)
{
genType tmp(v);
genType xhalf(tmp * genType(0.5f));
genUType i = *reinterpret_cast<genUType*>(const_cast<genType*>(&v));
i = genUType(0x5f375a86) - (i >> genUType(1));
tmp = *reinterpret_cast<genType*>(&i);
tmp = tmp * (genType(1.5f) - xhalf * tmp * tmp);
return tmp;
}
}
template <>
GLM_FUNC_QUALIFIER lowp_vec1 inversesqrt(lowp_vec1 const & v)
{
float tmp(v.x);
float xhalf(0.5f * tmp);
uint i = *reinterpret_cast<uint*>(const_cast<lowp_vec1*>(&v));
i = 0x5f375a86 - (i >> 1);
tmp = *reinterpret_cast<float*>(i);
tmp = tmp * (1.5f - xhalf * tmp * tmp);
return lowp_vec1(tmp);
return detail::fastInversesqrt<lowp_vec1, uint>(v);
}
template <>
GLM_FUNC_QUALIFIER lowp_vec2 inversesqrt(lowp_vec2 const & v)
{
lowp_vec2 tmp(v);
lowp_vec2 xhalf(0.5f * tmp);
lowp_uvec2 i = *reinterpret_cast<lowp_uvec2*>(const_cast<lowp_vec2*>(&v));
i = lowp_uvec2(0x5f375a86) - (i >> lowp_uvec2(1));
tmp = *reinterpret_cast<lowp_vec2*>(&i);
tmp = tmp * (1.5f - xhalf * tmp * tmp);
return tmp;
return detail::fastInversesqrt<lowp_vec2, lowp_uvec2>(v);
}
template <>
GLM_FUNC_QUALIFIER lowp_vec3 inversesqrt(lowp_vec3 const & v)
{
lowp_vec3 tmp(v);
lowp_vec3 xhalf(0.5f * tmp);
lowp_uvec3 i = *reinterpret_cast<lowp_uvec3*>(const_cast<lowp_vec3*>(&v));
i = lowp_uvec3(0x5f375a86) - (i >> lowp_uvec3(1));
tmp = *reinterpret_cast<lowp_vec3*>(&i);
tmp = tmp * (1.5f - xhalf * tmp * tmp);
return tmp;
return detail::fastInversesqrt<lowp_vec3, lowp_uvec3>(v);
}
template <>
GLM_FUNC_QUALIFIER lowp_vec4 inversesqrt(lowp_vec4 const & v)
{
lowp_vec4 tmp(v);
lowp_vec4 xhalf(0.5f * tmp);
lowp_uvec4 i = *reinterpret_cast<lowp_uvec4*>(const_cast<lowp_vec4*>(&v));
i = lowp_uvec4(0x5f375a86) - (i >> lowp_uvec4(1));
tmp = *reinterpret_cast<lowp_vec4*>(&i);
tmp = tmp * (1.5f - xhalf * tmp * tmp);
return tmp;
return detail::fastInversesqrt<lowp_vec4, lowp_uvec4>(v);
}
}//namespace glm

10
glm/gtx/fast_square_root.inl
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@ -30,15 +30,7 @@ namespace glm
genType const & x
)
{
genType tmp = x;
float xhalf = 0.5f * float(tmp);
uint i = *(uint*)&x;
i = 0x5f375a86 - (i >> 1);
//x = *(float*)&i;
//x = *((float*)(char*)&i);
tmp = detail::uif32(i).f;
tmp = tmp * (1.5f - xhalf * tmp * tmp);
return genType(tmp);
return detail::fastInversesqrt<genType, uint>(x);
}
VECTORIZE_VEC(fastInverseSqrt)