Keyframe_points not set in right place #83051

New Issue

burger@wiredworks.com · 2020-11-26T14:01:31+01:00

2020-11-26 14:01:31 +01:00

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: Quadro K2000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 385.69

Blender Version
Broken: version: 2.83.4, branch: master, commit date: 2020-08-05 06:00, hash: c113af8288
Worked: (newest version of Blender that worked as expected)

Short description of error

Point not set at specified Coordinate

Exact steps for others to reproduce the error
Default startup with Cube

A simple script not setting the keyframe_points to the specified coordinates

import bpy

Dataobject = bpy.data.objects['Cube']
Dataobject['Jrk'] = 0

fcurve = Dataobject.driver_add('["Jrk"]')
- THX to Philipp Oeser (lichtwerk)
- to edit the driver fcurve with keyframes, you'll have to remove the fmodifier
try:
    fcurve.modifiers.remove(fcurve.modifiers[0])
except IndexError:
     pass
 
fcurve.keyframe_points.insert(0,0)
fcurve.keyframe_points.insert(0.01,1)
fcurve.keyframe_points.insert(0.02,1)
fcurve.keyframe_points.insert(0.03,0)

for i in range(0, len(fcurve.keyframe_points)):
    try:
        fcurve.keyframe_points[i].handle_left  = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])
        fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])  
    except IndexError:
        pass

With slightly larger values it works

import bpy

Dataobject = bpy.data.objects['Cube']
Dataobject['Jrk'] = 0

fcurve = Dataobject.driver_add('["Jrk"]')
- THX to Philipp Oeser (lichtwerk)
- to edit the driver fcurve with keyframes, you'll have to remove the fmodifier
try:
    fcurve.modifiers.remove(fcurve.modifiers[0])
except IndexError:
     pass
 
fcurve.keyframe_points.insert(0,0)
fcurve.keyframe_points.insert(0.1,0.1)
fcurve.keyframe_points.insert(0.15,0.1)
fcurve.keyframe_points.insert(0.2,0)

for i in range(0, len(fcurve.keyframe_points)):
    try:
        fcurve.keyframe_points[i].handle_left  = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])
        fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])  
    except IndexError:
        pass

**System Information** Operating system: Windows-7-6.1.7601-SP1 64 Bits Graphics card: Quadro K2000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 385.69 **Blender Version** Broken: version: 2.83.4, branch: master, commit date: 2020-08-05 06:00, hash: `c113af8288` Worked: (newest version of Blender that worked as expected) **Short description of error** Point not set at specified Coordinate **Exact steps for others to reproduce the error** Default startup with Cube A simple script not setting the keyframe_points to the specified coordinates ``` import bpy Dataobject = bpy.data.objects['Cube'] Dataobject['Jrk'] = 0 fcurve = Dataobject.driver_add('["Jrk"]') - THX to Philipp Oeser (lichtwerk) - to edit the driver fcurve with keyframes, you'll have to remove the fmodifier try: fcurve.modifiers.remove(fcurve.modifiers[0]) except IndexError: pass fcurve.keyframe_points.insert(0,0) fcurve.keyframe_points.insert(0.01,1) fcurve.keyframe_points.insert(0.02,1) fcurve.keyframe_points.insert(0.03,0) for i in range(0, len(fcurve.keyframe_points)): try: fcurve.keyframe_points[i].handle_left = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) except IndexError: pass ``` ![keyframe3.png](https://archive.blender.org/developer/F9380726/keyframe3.png) With slightly larger values it works ``` import bpy Dataobject = bpy.data.objects['Cube'] Dataobject['Jrk'] = 0 fcurve = Dataobject.driver_add('["Jrk"]') - THX to Philipp Oeser (lichtwerk) - to edit the driver fcurve with keyframes, you'll have to remove the fmodifier try: fcurve.modifiers.remove(fcurve.modifiers[0]) except IndexError: pass fcurve.keyframe_points.insert(0,0) fcurve.keyframe_points.insert(0.1,0.1) fcurve.keyframe_points.insert(0.15,0.1) fcurve.keyframe_points.insert(0.2,0) for i in range(0, len(fcurve.keyframe_points)): try: fcurve.keyframe_points[i].handle_left = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) except IndexError: pass ``` ![keyframe4.png](https://archive.blender.org/developer/F9380780/keyframe4.png)

burger@wiredworks.com commented

2020-11-26 14:01:31 +01:00

Added subscriber: @martburg

Robert Guetzkow commented

2020-11-26 14:22:49 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2020-11-26 14:22:49 +01:00

Is this a different issue to #83044?

burger@wiredworks.com commented

2020-11-26 14:29:06 +01:00

Yes, different issue !

More explanation: There seems to be some graininess along the timeline. The Time of Keyframes can not be set with high precision.

Yes, different issue ! More explanation: There seems to be some graininess along the timeline. The Time of Keyframes can not be set with high precision.

burger@wiredworks.com commented

2020-11-26 17:49:15 +01:00

Running the script:

import bpy
import numpy as np

Dataobject = bpy.data.objects['Cube']
Dataobject['Jrk'] = 0

fcurve = Dataobject.driver_add('["Jrk"]')
- THX to Philipp Oeser (lichtwerk)
- to edit the driver fcurve with keyframes, you'll have to remove the fmodifier
try:
    fcurve.modifiers.remove(fcurve.modifiers[0])
except IndexError:
     pass

X  = np.linspace(0.001 , 1.001, num = 1000, retstep = False, dtype = np.double)
Y  = np.zeros(1000, dtype = np.double)
          
for i in range(0,len(X)):
    fcurve.keyframe_points.insert( X[i] ,Y[i]+0.001)
    
print(len(X))
print(len(fcurve.keyframe_points))

Confirms IMHO that keyframe points have to be spaced 0.01 units apart and have to start at 0, on the X (time axis) and the Y-axis is showing glitches as well

THX
Martin

Running the script: ``` import bpy import numpy as np Dataobject = bpy.data.objects['Cube'] Dataobject['Jrk'] = 0 fcurve = Dataobject.driver_add('["Jrk"]') - THX to Philipp Oeser (lichtwerk) - to edit the driver fcurve with keyframes, you'll have to remove the fmodifier try: fcurve.modifiers.remove(fcurve.modifiers[0]) except IndexError: pass X = np.linspace(0.001 , 1.001, num = 1000, retstep = False, dtype = np.double) Y = np.zeros(1000, dtype = np.double) for i in range(0,len(X)): fcurve.keyframe_points.insert( X[i] ,Y[i]+0.001) print(len(X)) print(len(fcurve.keyframe_points)) ``` ![keyframe6.png](https://archive.blender.org/developer/F9382000/keyframe6.png) Confirms IMHO that keyframe points have to be spaced 0.01 units apart and have to start at 0, on the X (time axis) and the Y-axis is showing glitches as well THX Martin

Sybren A. Stüvel commented

2020-11-27 12:37:06 +01:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2020-11-27 12:37:06 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Sybren A. Stüvel commented

2020-11-27 12:37:06 +01:00

The bug report is incomplete, as there is no "Short description of error" filled out. What exactly is the problem?

        fcurve.keyframe_points[i].handle_left  = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])
        fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1])

What is the use of this code? Placing the handles right on top of the keyframe points is not mathematically valid, as then there is no defined slope at that point.

Keyframes are stored with float precision, so there is a numerical limit. This in itself is not a bug.

The bug report is incomplete, as there is no "**Short description of error**" filled out. What exactly is the problem? ``` fcurve.keyframe_points[i].handle_left = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) fcurve.keyframe_points[i].handle_right = (fcurve.keyframe_points[i].co[0],fcurve.keyframe_points[i].co[1]) ``` What is the use of this code? Placing the handles right on top of the keyframe points is not mathematically valid, as then there is no defined slope at that point. Keyframes are stored with `float` precision, so there is a numerical limit. This in itself is not a bug.

burger@wiredworks.com commented

2020-11-27 17:10:05 +01:00

OK, simpler script

import bpy

Dataobject = bpy.data.objects['Cube']
Dataobject['Jrk'] = 0

fcurve = Dataobject.driver_add('["Jrk"]')
- THX to Philipp Oeser (lichtwerk)
- to edit the driver fcurve with keyframes, you'll have to remove the fmodifier
try:
    fcurve.modifiers.remove(fcurve.modifiers[0])
except IndexError:
     pass
 
fcurve.keyframe_points.insert(0,0)
fcurve.keyframe_points.insert(0.01,1)
fcurve.keyframe_points.insert(0.02,1)
fcurve.keyframe_points.insert(0.03,0)

print(len(fcurve.keyframe_points))

The Point at (0,0) is not set and the Point at (0.03, 0) is also not set. and (len(fcurve.keyframe_points)) = 2

OK, simpler script ``` import bpy Dataobject = bpy.data.objects['Cube'] Dataobject['Jrk'] = 0 fcurve = Dataobject.driver_add('["Jrk"]') - THX to Philipp Oeser (lichtwerk) - to edit the driver fcurve with keyframes, you'll have to remove the fmodifier try: fcurve.modifiers.remove(fcurve.modifiers[0]) except IndexError: pass fcurve.keyframe_points.insert(0,0) fcurve.keyframe_points.insert(0.01,1) fcurve.keyframe_points.insert(0.02,1) fcurve.keyframe_points.insert(0.03,0) print(len(fcurve.keyframe_points)) ``` ![Keyframe9.png](https://archive.blender.org/developer/F9390695/Keyframe9.png) The Point at (0,0) is not set and the Point at (0.03, 0) is also not set. and (len(fcurve.keyframe_points)) = 2

Sybren A. Stüvel commented

2020-11-30 13:35:13 +01:00

Changed status from 'Needs User Info' to: 'Archived'

Sybren A. Stüvel closed this issue

2020-11-30 13:35:13 +01:00

Sybren A. Stüvel commented

2020-11-30 13:35:13 +01:00

You have hit the minimal distance between keyframes. See BEZT_BINARYSEARCH_THRESH as defined in BKE_fcurve.h:

#define BEZT_BINARYSEARCH_THRESH 0.01f

This was introduced 7 years ago (76dd3db304), so it's quite safe to assume that this is how Blender behaves.

What do you need such small numbers for anyway? With this kind of curve, it's probably a better choice to set it for constant interpolation instead:

key = fcurve.keyframe_points.insert(-1, 1)
key.interpolation = 'CONSTANT'

key = fcurve.keyframe_points.insert(0, 0)
key.interpolation = 'CONSTANT'

This will give the same sharp dropoff as your code seems to intend:

You have hit the minimal distance between keyframes. See `BEZT_BINARYSEARCH_THRESH` as defined in `BKE_fcurve.h`: ``` #define BEZT_BINARYSEARCH_THRESH 0.01f ``` This was introduced 7 years ago (76dd3db304), so it's quite safe to assume that this is how Blender behaves. What do you need such small numbers for anyway? With this kind of curve, it's probably a better choice to set it for constant interpolation instead: ``` key = fcurve.keyframe_points.insert(-1, 1) key.interpolation = 'CONSTANT' key = fcurve.keyframe_points.insert(0, 0) key.interpolation = 'CONSTANT' ``` This will give the same sharp dropoff as your code seems to intend: ![image.png](https://archive.blender.org/developer/F9414061/image.png)

burger@wiredworks.com commented

2020-11-30 14:21:10 +01:00

The curve I intend to generate is the Jerk Component of a move

Acceleration, Velocity, and Position are the respective Integrals of that Jerk so being able to use smaller values would be a nice to have.
THX, for looking into the Problem and providing the Location in the source.

I'm not sure about the mathematical validness --- If the fcurves are close to Beziers - setting the control handle points to the same value as the point is valid it just reduces the degree of the Bezier

and I'm also no sure about the formulation of "as then there is no defined slope at that point" we then have a left slope and a right slope and they are coincident with the graph of the linear interpolation

THX
Martin

The curve I intend to generate is the Jerk Component of a move ![Move1.png](https://archive.blender.org/developer/F9414174/Move1.png) Acceleration, Velocity, and Position are the respective Integrals of that Jerk so being able to use smaller values would be a nice to have. THX, for looking into the Problem and providing the Location in the source. I'm not sure about the mathematical validness --- If the fcurves are close to Beziers - setting the control handle points to the same value as the point is valid it just reduces the degree of the Bezier and I'm also no sure about the formulation of "as then there is no defined slope at that point" we then have a left slope and a right slope and they are coincident with the graph of the linear interpolation THX Martin

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Keyframe_points not set in right place #83051