As an inherent property of matrix-based transformation math, non-
uniform scaling of a parent bone induces shear into the transform
matrix of any rotated child. Such matrices cannot be cleanly
decomposed into a combination of location/rotation/scale, which
causes issues for rigging and animation tools.
Blender bones have options to exclude rotation and/or scale from the
inherited transformation, but don't have any support for removing the
often undesired shear component. That goal requires replacing simple
parenting with a combination of multiple bones and constraints. The
same is true about the goal of inheriting some scale, but completely
avoiding shear.
This patch replaces the old Inherit Scale checkbox with a enum that
supports multiple options:
* Full: inherit all effects of scale, like with enabled Inherit Scale.
* Fix Shear: removes shear from the final inherited transformation.
The cleanup math is specifically designed to preserve the main
axis of the bone, its length and total volume, and minimally
affect roll on average. It however will not prevent reappearance
of shear due to local rotation of the child or its children.
* Average: inherit uniform scale that represents the parent volume.
This is the simplest foolproof solution that will inherit some
scale without ever causing shear.
* None: completely remove scale and shear.
* None (Legacy): old disabled Inherit Scale checkbox.
This mode does not handle parent shear in any way, so the child
is likely to end up having both scale and shear. It is retained
for backward compatibility.
Since many rigging-related addons access the use_inherit_scale
property from Python, it is retained as a backward compatibility
stub that provides the old functionality.
As a side effect of reworking the code, this also fixes a matrix
multiplication order bug in the Inherit Rotation code, which caused
the parent local scale to be applied in world space. In rigger
opinion this option is useless in production rigs, so this fix
should not be a problem.
Reviewers: brecht
Differential Revision: https://developer.blender.org/D5588
matrix inversion was changed in rB01c75c3765eb from own code to EIGEN
for performance reasons. EIGEN would return a zero matrix on failure
(resulting in the pivot always being at the object origin).
This brings back the "old" matrix inversion code (which has the benifit
of providing a partial solution which makes the local transform center
appear correct)
Reviewers: campbellbarton
Maniphest Tasks: T57767
Differential Revision: https://developer.blender.org/D4804
Unlike location and rotation, there is a meaningful definition of
overall/average scaling via the total change in the volume. This
adds an option to retrieve that via a single driver variable,
instead of having to use three and an expression.
Using the determinant to compute the volume scaling also allows
detecting flipping due to negative scale - this is impossible
to do via the three variable approach.
The volume_scale functions are added purely for code readability:
'volume scale factor' is easier to understand than determinant.
Differential Revision: https://developer.blender.org/D4803
Previously B-Bone deformation mapped every vertex to just one
B-Bone segment. This results in abrupt transformation differences
between the sides of each threshold plane, reducing the quality
of B-Bone deformation and making the use of shape keys impractical.
This commit replaces this approach with a linear blend between
the two closest segment transformations, effectively representing
the B-Bone as two weight-blended plain bones for each vertex.
In order to distribute the interpolation more evenly along the
bone, segment matrices for deformation are now computed at points
between the segments and at the ends of the B-Bone. The computation
also uses the true tangents of the Bezier curve for the orientation.
The nodes at the end of the bone require some special handling to
deal with zero-length Bezier handles caused by a zero ease value.
The Copy Transforms constraint now also smoothly interpolates
rotation and scaling along the bone shape when enabled.
The initial version of the patch was submitted by @Sam200.
Differential Revision: https://developer.blender.org/D4635
BF-admins agree to remove header information that isn't useful,
to reduce noise.
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This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
- Remove 'rotate_m2', unlike 'rotate_m4' it created a new matrix
duplicating 'angle_to_mat2' - now used instead.
(better avoid matching functions having different behavior).
- Add 'axis_angle_to_mat4_single',
convenience wrapper for 'axis_angle_to_mat3_single'.
- Replace 'unit_m4(), rotate_m4()' with a single call to 'axis_angle_to_mat4_single'.
mul_m4_m4m4(R, A, B) gives us R = AB in general. Existing code assumed the worst, that A and B both alias the output R. For safety it makes internal copies of A and B before calculating & writing R.
This is the least common case. Usually all 3 matrices differ. Often we see M = AM or M = MB, but never M = MM.
With this revision mul_m4_m4m4 is called in exactly the same way but copies inputs only when needed. If you know the inputs are independent of the output use the "uniq" variant to skip the saftety checks.
mat3_polar_decompose gives the right polar decomposition of given matrix,
as a pair (U, P) of matrices.
interp_m3_m3m3 uses that polar decomposition to perform a correct matrix interpolation,
even with non-uniformly scaled ones (where blend_m3_m3m3 would fail).
interp_m4_m4m4 just adds translation interpolation to the _m3 variant.
`BLI_space_transform_from_matrices()` defines a 'global-invariant' transform
(same point in global space, two different coordinates in local and target spaces).
New `BLI_space_transform_global_from_matrices()` is kind of opposite, it defines
a 'local-invariant' transform (two different points in global space, same coordinates in local and target spaces).
Useful to 'match' meshes.
It still warns the user that there may be an error, but the baking goes
on. Also using the new is_uniform_scaled_m4() instead of float comparison.
Reported and fix suggested by Campbell Barton as a concern over 2bfc3deb
Issue was caused by inverting a degenerate matrix when
evaluating drivers.
Solved by using tweaked inverse code (same as used in Cycles).
Should have no affect on cases when matrix is not degenerate.
