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Fix #119703: Incorrect conversion of identity quaternion to axis angle #119762

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Iliya Katushenock wants to merge 12 commits from mod_moder/blender:fix_119703 into main
pull from: mod_moder/blender:fix_119703
merge into: blender:main

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Conversation 0 Commits 12 Files Changed 2 +23 -2
2 changed files with 23 additions and 2 deletions
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7
source/blender/blenlib/BLI_math_quaternion.hh
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@ -630,8 +630,11 @@ AxisAngleBase<T, AngleT> to_axis_angle(const QuaternionBase<T> &quat)
T sin_half_angle = math::length(axis); T sin_half_angle = math::length(axis);
/* Prevent division by zero for axis conversion. */ /* Prevent division by zero for axis conversion. */
if (sin_half_angle < T(0.0005)) { if (sin_half_angle < T(0.0005)) {
sin_half_angle = T(1); const AxisAngleBase<T, AngleT>::vec3_type identity_axis =
axis[1] = T(1); AxisAngleBase<T, AngleT>::identity().axis();
BLI_assert(abs(cos_half_angle) > 0.0005);
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Clément Foucault commented 2024-05-14 23:07:06 +02:00
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Use AngleT(0).

sign will return 0 if cos_half_angle is 0. Is that what you want?

Use `AngleT(0)`. `sign` will return `0` if `cos_half_angle` is 0. Is that what you want?
Iliya Katushenock commented 2024-05-14 23:14:02 +02:00
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No, i expect that sign will always be non zero... But here this looks like its will be enough to just add assertion. This is safe for normalized quaternion.

No, i expect that `sign` will always be non zero... But here this looks like its will be enough to just add assertion. This is safe for normalized quaternion.
AxisAngleBase<T, AngleT> identity(identity_axis * sign(cos_half_angle), AngleT(0));
return identity;
} }
/* Normalize the axis. */ /* Normalize the axis. */
axis /= sin_half_angle; axis /= sin_half_angle;

18
source/blender/blenlib/tests/BLI_math_rotation_test.cc
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@ -879,4 +879,22 @@ TEST(math_rotation, DualQuaternionTransform)
} }
} }
TEST(math_axis_angle, AxisAngleFromQuaternion)
{
{
const math::AxisAngle axis_angle({0.0f, 1.0f, 0.0f}, math::AngleRadian(0));
const math::Quaternion quaternion(1.0f, {0.0f, 0.0f, 0.0f});
const math::AxisAngle from_quaternion = math::to_axis_angle(quaternion);
EXPECT_V3_NEAR(axis_angle.axis(), from_quaternion.axis(), 1e-6);
EXPECT_NEAR(axis_angle.angle().radian(), from_quaternion.angle().radian(), 1e-6);
}
{
const math::AxisAngle axis_angle({0.0f, -1.0f, 0.0f}, math::AngleRadian(0));
const math::Quaternion quaternion(-1.0f, {0.0f, 0.0f, 0.0f});
const math::AxisAngle from_quaternion = math::to_axis_angle(quaternion);
EXPECT_V3_NEAR(axis_angle.axis(), from_quaternion.axis(), 1e-6);
EXPECT_NEAR(axis_angle.angle().radian(), from_quaternion.angle().radian(), 1e-6);
}
}
} // namespace blender::math::tests } // namespace blender::math::tests