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Fix T73117: B-Bone twist weirdness in chains with sharp bends. 

When computing the roll value coming from the handle bone, the code
was using some strange unexplained math. It probably works fine when
the difference with the 'zero roll' orientation is pure twist, like
is the case when called from mat3_to_vec_roll. However, it appears
to break when significant swing is involved.

The issue is fixed by using the proper Swing+Twist decomposition
utility function that was added in a recent version for drivers.
This commit is contained in:
Alexander Gavrilov 2020-01-19 18:44:00 +03:00
parent 3e11c4e63b
commit d1657b406e
Notes: blender-bot 2023-02-13 23:43:14 +01:00 
Referenced by issue #82930, bpy.types.Bone.AxisRollFromMatrix() returns bad roll value
Referenced by issue #73840, Broken Shrinkwrap Modifier (and Bendy Bones)
Referenced by issue #73117, b-bones interpolation error
1 changed files with 6 additions and 2 deletions
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8
source/blender/blenkernel/intern/armature.c
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@ -2293,13 +2293,17 @@ void mat3_to_vec_roll(const float mat[3][3], float r_vec[3], float *r_roll)
* If vec is the Y vector from purely rotational mat, result should be exact. */
void mat3_vec_to_roll(const float mat[3][3], const float vec[3], float *r_roll)
{
float vecmat[3][3], vecmatinv[3][3], rollmat[3][3];
float vecmat[3][3], vecmatinv[3][3], rollmat[3][3], q[4];
/* Compute the orientation relative to the vector with zero roll. */
vec_roll_to_mat3(vec, 0.0f, vecmat);
invert_m3_m3(vecmatinv, vecmat);
mul_m3_m3m3(rollmat, vecmatinv, mat);
*r_roll = atan2f(rollmat[2][0], rollmat[2][2]);
/* Extract the twist angle as the roll value. */
mat3_to_quat(q, rollmat);
*r_roll = quat_split_swing_and_twist(q, 1, NULL, NULL);
}
/* Calculates the rest matrix of a bone based on its vector and a roll around that vector. */