MatrixUtils LERP incorrect interpolation #51287

New Issue

Dolphin Dream · 2017-04-22T05:25:26+02:00

Dolphin Dream commented

2017-04-22 05:25:26 +02:00

System Information
MacBook Pro
Processor 2.2 GHz Intel Core i7
Memory 16 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6750M 1024 MB
Software OS X 10.12.3 - Sierra

Blender Version
2.78a (e8299c8)

Short description of error
When doing matrix interpolation with matrixutils lerp function for certain matrices the interpolation seems to give the wrong results.

Exact steps for others to reproduce the error
Type these in blender console or use within a script..

import mathutils
m1 = Quaternion((1,1,1,1)).to_matrix().to_4x4()
m2 = Matrix()
m1
m2
m2.lerp(m1,0)
m2.lerp(m1,1)
m1.lerp(m2,0)
m1.lerp(m2,1)

the terminal output:

>>> import mathutils
>>> m1 = Quaternion((1,1,1,1)).to_matrix().to_4x4()
>>> m2 = Matrix()
>>> m1

Matrix(((-3.0, 0.0, 4.0, 0.0),
        (4.0, -3.0, 0.0, 0.0),
        (0.0, 4.0, -3.0, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

>>> m2

Matrix(((1.0, 0.0, 0.0, 0.0),
        (0.0, 1.0, 0.0, 0.0),
        (0.0, 0.0, 1.0, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

>>> m2.lerp(m1,0)

Matrix(((1.0, 0.0, 0.0, 0.0),
        (0.0, 1.0, 0.0, 0.0),
        (0.0, 0.0, 1.0, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

>>> m2.lerp(m1,1)

Matrix(((-2.1428568363189697, -1.428571343421936, 4.285714149475098, 0.0),
        (4.285714149475098, -2.1428568363189697, 1.428571343421936, 0.0),
        (1.428571343421936, 4.285714149475098, 2.142857074737549, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

>>> m1.lerp(m2,0)

Matrix(((-2.1428568363189697, -1.428571343421936, 4.285714149475098, 0.0),
        (4.285714149475098, -2.1428568363189697, 1.428571343421936, 0.0),
        (1.428571343421936, 4.285714149475098, 2.142857074737549, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

>>> m1.lerp(m2,1)

Matrix(((1.0, 0.0, 0.0, 0.0),
        (0.0, 1.0, 0.0, 0.0),
        (0.0, 0.0, 1.0, 0.0),
        (0.0, 0.0, 0.0, 1.0)))

I would expect that m2.lerp(m1, 1) should give m1 (which is is not the case)
I would expect that m1.lerp(m2, 0) should give m1 (which is is not the case)

**System Information** MacBook Pro Processor 2.2 GHz Intel Core i7 Memory 16 GB 1333 MHz DDR3 Graphics AMD Radeon HD 6750M 1024 MB Software OS X 10.12.3 - Sierra **Blender Version** 2.78a (e8299c8) **Short description of error** When doing matrix interpolation with matrixutils lerp function for certain matrices the interpolation seems to give the wrong results. **Exact steps for others to reproduce the error** Type these in blender console or use within a script.. ``` import mathutils m1 = Quaternion((1,1,1,1)).to_matrix().to_4x4() m2 = Matrix() m1 m2 m2.lerp(m1,0) m2.lerp(m1,1) m1.lerp(m2,0) m1.lerp(m2,1) the terminal output: >>> import mathutils >>> m1 = Quaternion((1,1,1,1)).to_matrix().to_4x4() >>> m2 = Matrix() >>> m1 Matrix(((-3.0, 0.0, 4.0, 0.0), (4.0, -3.0, 0.0, 0.0), (0.0, 4.0, -3.0, 0.0), (0.0, 0.0, 0.0, 1.0))) >>> m2 Matrix(((1.0, 0.0, 0.0, 0.0), (0.0, 1.0, 0.0, 0.0), (0.0, 0.0, 1.0, 0.0), (0.0, 0.0, 0.0, 1.0))) >>> m2.lerp(m1,0) Matrix(((1.0, 0.0, 0.0, 0.0), (0.0, 1.0, 0.0, 0.0), (0.0, 0.0, 1.0, 0.0), (0.0, 0.0, 0.0, 1.0))) >>> m2.lerp(m1,1) Matrix(((-2.1428568363189697, -1.428571343421936, 4.285714149475098, 0.0), (4.285714149475098, -2.1428568363189697, 1.428571343421936, 0.0), (1.428571343421936, 4.285714149475098, 2.142857074737549, 0.0), (0.0, 0.0, 0.0, 1.0))) >>> m1.lerp(m2,0) Matrix(((-2.1428568363189697, -1.428571343421936, 4.285714149475098, 0.0), (4.285714149475098, -2.1428568363189697, 1.428571343421936, 0.0), (1.428571343421936, 4.285714149475098, 2.142857074737549, 0.0), (0.0, 0.0, 0.0, 1.0))) >>> m1.lerp(m2,1) Matrix(((1.0, 0.0, 0.0, 0.0), (0.0, 1.0, 0.0, 0.0), (0.0, 0.0, 1.0, 0.0), (0.0, 0.0, 0.0, 1.0))) ``` I would expect that m2.lerp(m1, 1) should give m1 (which is is not the case) I would expect that m1.lerp(m2, 0) should give m1 (which is is not the case) ![matrixutils-lerp-bug.png](https://archive.blender.org/developer/F566755/matrixutils-lerp-bug.png)

Dolphin Dream commented

2017-04-22 05:25:26 +02:00

Changed status to: 'Open'

Dolphin Dream commented

2017-04-22 05:25:26 +02:00

Added subscriber: @MariusGiurgi

Brecht Van Lommel commented

2017-04-22 14:49:09 +02:00

Added subscribers: @ideasman42, @brecht

Brecht Van Lommel commented

2017-04-22 14:49:09 +02:00

@ideasman42, the issue is that blend_m4_m4m4 assumes there is no shearing in the matrix, only scaling. Switching to interp_m4_m4m4 solves the problem but relies on Eigen, which means it can't work with MATH_STANDALONE.

@ideasman42, the issue is that `blend_m4_m4m4` assumes there is no shearing in the matrix, only scaling. Switching to `interp_m4_m4m4` solves the problem but relies on Eigen, which means it can't work with `MATH_STANDALONE`.

Campbell Barton commented

2017-05-08 06:41:19 +02:00

@brecht - if interp_m4_m4m4 resolves we better use it. MATH_STANDALONE allows mathutils to be build as a stand-alone C module, but shouldn't hold back fixes from going in.

Even for that use-case, the stand-alone module can use Eigen.

@brecht - if `interp_m4_m4m4` resolves we better use it. `MATH_STANDALONE` allows mathutils to be build as a stand-alone C module, but shouldn't hold back fixes from going in. Even for that use-case, the stand-alone module can use Eigen.

Campbell Barton commented

2017-05-26 08:58:17 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2017-05-26 08:58:17 +02:00

blender-admin commented

2017-05-26 09:00:20 +02:00

This issue was referenced by 98df7d778f

This issue was referenced by 98df7d778f8b9318388bf24ab6be3b4930ef2f6f

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MatrixUtils LERP incorrect interpolation #51287