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Improved lerp implementation.

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This commit is contained in:
Бранимир Караџић
2020-04-04 09:56:16 -07:00
parent af9ccfdf56
commit 936327aa0f
3 changed files with 21 additions and 1 deletions
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11
include/bx/inline/math.inl
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@@ -124,7 +124,11 @@ namespace bx
inline BX_CONSTEXPR_FUNC float lerp(float _a, float _b, float _t)
{
return _a + (_b - _a) * _t;
// Reference(s):
// - Linear interpolation past, present and future
// https://web.archive.org/web/20200404165201/https://fgiesen.wordpress.com/2012/08/15/linear-interpolation-past-present-and-future/
//
return mad(_t, _b, nms(_t, _a, _a) );
}
inline BX_CONSTEXPR_FUNC float invLerp(float _a, float _b, float _value)
@@ -277,6 +281,11 @@ namespace bx
return _a - trunc(_a);
}
inline BX_CONSTEXPR_FUNC float nms(float _a, float _b, float _c)
{
return _c - _a * _b;
}
inline BX_CONSTEXPR_FUNC float mad(float _a, float _b, float _c)
{
return _a * _b + _c;

4
include/bx/math.h
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@@ -249,6 +249,10 @@ namespace bx
///
BX_CONSTEXPR_FUNC float fract(float _a);
/// Returns result of negated multiply-sub operation -(_a * _b - _c).
///
BX_CONSTEXPR_FUNC float nms(float _a, float _b, float _c);
/// Returns result of multipla and add (_a * _b + _c).
///
BX_CONSTEXPR_FUNC float mad(float _a, float _b, float _c);

7
tests/math_test.cpp
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@@ -196,6 +196,13 @@ TEST_CASE("ToBits", "")
REQUIRE(UINT64_C(0x123456789abcdef0) == bx::doubleToBits(bx::bitsToDouble(UINT32_C(0x123456789abcdef0) ) ) );
}
TEST_CASE("lerp", "")
{
REQUIRE(1389.0f == bx::lerp(1389.0f, 1453.0f, 0.0f) );
REQUIRE(1453.0f == bx::lerp(1389.0f, 1453.0f, 1.0f) );
REQUIRE(0.5f == bx::lerp(0.0f, 1.0f, 0.5f) );
}
void mtxCheck(const float* _a, const float* _b)
{
if (!bx::equal(_a, _b, 16, 0.01f) )