static float CalculateMidPercent(const SplineControlNode& start,
const SplineControlNode& end) {
// The mid value we called 'k' in the dual cubic documentation.
// It's between 0~1 and determines where the start and end cubics are joined
// along the x-axis.
const Range valid_range = CalculateValidMidRange(start, end);
// Return the part of the range closest to the half-way mark. This seems to
// generate the smoothest looking curves.
const float mid_unclamped = valid_range.Clamp(0.5f);
// Clamp away from 0 and 1. The math requires the mid node to be strictly
// between 0 and 1. If we get to close to 0 or 1, some divisions are going to
// explode and we'll lose numerical precision.
const float mid =
mathfu::Clamp(mid_unclamped, kMinMidPercent, kMaxMidPercent);
return mid;
}
// Clamping values inside the range should result in the same value.
TEST_F(RangeTests, Clamp_Border) {
const Range zero_one(0.0f, 1.0f);
EXPECT_EQ(0.0f, zero_one.Clamp(0.0f));
EXPECT_EQ(1.0f, zero_one.Clamp(1.0f));
}
// Clamping values inside the range should result in the same value.
TEST_F(RangeTests, Clamp_Inside) {
const Range zero_one(0.0f, 1.0f);
EXPECT_EQ(0.5f, zero_one.Clamp(0.5f));
EXPECT_EQ(0.9999999f, zero_one.Clamp(0.9999999f));
}
// Clamping values to the full range should always return the original value.
TEST_F(RangeTests, Clamp_ToInfinity) {
const Range full(-kInf, kInf);
EXPECT_EQ(kInf, full.Clamp(kInf));
EXPECT_EQ(1.0f, full.Clamp(1.0f));
EXPECT_EQ(-kInf, full.Clamp(-kInf));
}
// Passing infinity into a range should clamp fine.
TEST_F(RangeTests, Clamp_Infinity) {
const Range zero_one(0.0f, 1.0f);
EXPECT_EQ(1.0f, zero_one.Clamp(kInf));
EXPECT_EQ(0.0f, zero_one.Clamp(-kInf));
}
// Clamping values inside the range should result in the same value.
TEST_F(RangeTests, Clamp_Outside) {
const Range zero_one(0.0f, 1.0f);
EXPECT_EQ(0.0f, zero_one.Clamp(-1.0f));
EXPECT_EQ(1.0f, zero_one.Clamp(1.0000001f));
}