Action "Bouncing" when mixing automatic and manual action updates #45945

New Issue

mobious · 2015-08-29T07:14:12+02:00

mobious commented

2015-08-29 07:14:12 +02:00

System Information
Windows 7 64-bit
Intel HD Graphics 4000

Blender Version
Broken: 2.75 c6b042b

Files
action_bouncing.blend -- Contains a cube with a script that starts playing an action and manually updates the action's frame on alternating logic ticks. The animation frame rate is set to 1.

Short description of error
When an action is playing and the action's frame is manually set using setActionFrame() on alternating logic ticks and the action's play speed (playAction() speed argument multiplied by the Animation Frame Rate) is low, the "bounces" between the set frame and the start frame.

Exact steps for others to reproduce the error
Open the attached file and start the game engine. Note how the cube flickers between its starting position and its animated position. This jump to the action's start frame only occurs on logic ticks where the setActionFrame() method is not called and when the animation frame rate is relatively low. It occurs with less frequency as the animation frame rate is increased (either via the Animation Frame Rate option under the Properties tab or with the speed argument for playAction(). Also note that as the action continues to play, the bouncing will briefly stop during perios where the cubes current frame is behind the frame the action would be at if it was left to play by itself (i.e. if no calls made to setActionFrame()).

Additional Notes

It does not matter if the action is played on an object or armature.
The bouncing appears to stop after the point where the action would have finished if left to play by itself.
setActionFrame() must not be called on every logic tick for the bouncing to occur, i.e. you must skip some logic ticks by setting the Skip option on the Always sensor to some value greater than 0.

**System Information** Windows 7 64-bit Intel HD Graphics 4000 **Blender Version** Broken: 2.75 c6b042b **Files** [action_bouncing.blend](https://archive.blender.org/developer/F228894/action_bouncing.blend) -- Contains a cube with a script that starts playing an action and manually updates the action's frame on alternating logic ticks. The animation frame rate is set to 1. **Short description of error** When an action is playing and the action's frame is manually set using setActionFrame() on alternating logic ticks and the action's play speed (playAction() speed argument multiplied by the Animation Frame Rate) is low, the "bounces" between the set frame and the start frame. **Exact steps for others to reproduce the error** Open the attached file and start the game engine. Note how the cube flickers between its starting position and its animated position. This jump to the action's start frame only occurs on logic ticks where the setActionFrame() method is not called and when the animation frame rate is relatively low. It occurs with less frequency as the animation frame rate is increased (either via the Animation Frame Rate option under the Properties tab or with the speed argument for playAction(). Also note that as the action continues to play, the bouncing will briefly stop during perios where the cubes current frame is behind the frame the action would be at if it was left to play by itself (i.e. if no calls made to setActionFrame()). **Additional Notes** - It does not matter if the action is played on an object or armature. - The bouncing appears to stop after the point where the action would have finished if left to play by itself. - setActionFrame() must not be called on every logic tick for the bouncing to occur, i.e. you must skip some logic ticks by setting the Skip option on the Always sensor to some value greater than 0.

mobious commented

2015-08-29 07:14:13 +02:00

Changed status to: 'Open'

mobious commented

2015-08-29 07:14:13 +02:00

Added subscriber: @mobious

Sergey Sharybin commented

2015-09-01 12:21:38 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2015-09-01 12:21:38 +02:00

Not sure what exactly "bounding" and "flickers" means here, can you describe it a bit more?

Also, you're using original 2.75 release, please test 2.75a release and latest builds from builder.blender.org

Not sure what exactly "bounding" and "flickers" means here, can you describe it a bit more? Also, you're using original 2.75 release, please test 2.75a release and latest builds from builder.blender.org

mobious commented

2015-09-01 20:35:39 +02:00

By "bouncing", I mean that on a logic tick where I call setActionFrame(frameNumber), the cube will be place at position corresponding to frameNumber. On next logic tick (where setActionFrame() is not called) the cube is place at the position corresponding to the start frame value used in the original call to playAction().

This repeats every single time setActionFrame() is called on a logic tick and not called on the following logic tick, causing the cube to rappidly jump (e.g. visually flicker) back and forth between the two positions.

I tested it with the same results on 2.75a and the latest build from builder.blender.org, both with the exact same results. Did you download and run the file I attached? It should be obvious what the issue is when you run it.

By "bouncing", I mean that on a logic tick where I call setActionFrame(*frameNumber*), the cube will be place at position corresponding to *frameNumber*. On next logic tick (where setActionFrame() is not called) the cube is place at the position corresponding to the start frame value used in the original call to playAction(). This repeats every single time setActionFrame() is called on a logic tick and not called on the following logic tick, causing the cube to rappidly jump (e.g. visually flicker) back and forth between the two positions. I tested it with the same results on 2.75a and the latest build from builder.blender.org, both with the exact same results. Did you download and run the file I attached? It should be obvious what the issue is when you run it.

Sergey Sharybin commented

2015-09-02 09:38:57 +02:00

Yes, i've downloaded the file you attached. It just runs too fast here and not really clear if the "ghosting" effect there is a bug or some aspect of BGE.

At this point leaving this will leave the report up to BGE developers to fix the issue.

Yes, i've downloaded the file you attached. It just runs too fast here and not really clear if the "ghosting" effect there is a bug or some aspect of BGE. At this point leaving this will leave the report up to BGE developers to fix the issue.

Sergey Sharybin commented

2015-09-02 09:39:22 +02:00

Added subscribers: @brita, @hg1, @panzergame

mobious commented

2015-09-04 19:58:51 +02:00

I'm fairly certain that this is not the desired behavior for actions to have. Even if it was intentional, the behavior is inconsistent in its current implementation as the "bouncing" does not occur at higher animation playback speeds and will stop after the point were the action would have completed if left to play by itself.

To add to the discussion, the reason I discovered this bug was because I was trying to work around the fact that you currently cannot disable automatic animation updates by setting the play speed to 0. Instead, I set the play speed to a very low value which caused this bug to arise. Please take a look at this thread for some other improvements I think need to be made to the API with regard to action playback.

http://blenderartists.org/forum/showthread.php?379708-REQUEST-Improve-Python-interface-for-controlling-Actions

I'm fairly certain that this is not the desired behavior for actions to have. Even if it was intentional, the behavior is inconsistent in its current implementation as the "bouncing" does not occur at higher animation playback speeds and will stop after the point were the action would have completed if left to play by itself. To add to the discussion, the reason I discovered this bug was because I was trying to work around the fact that you currently cannot disable automatic animation updates by setting the play speed to 0. Instead, I set the play speed to a very low value which caused this bug to arise. Please take a look at this thread for some other improvements I think need to be made to the API with regard to action playback. http://blenderartists.org/forum/showthread.php?379708-REQUEST-Improve-Python-interface-for-controlling-Actions

Ulysse Martin commented

2015-09-20 20:27:45 +02:00

Added subscriber: @you.le

Ulysse Martin commented

2015-09-21 06:16:33 +02:00

If you comment line 409 in BL_Action.cpp: //m_calc_localtime = true; , the problem disappears... (maybe there's a modification to do in SetLocalTime function).

Ulysse Martin commented

2015-09-22 07:59:12 +02:00

After further investigations it seems that it is these lines which causes the problem in BL_Action.cpp Update function:

Grab the start time here so we don't end up with a negative m_localtime when suspending and resuming scenes.
if (m_starttime < 0)
m_starttime = curtime;

Because m_starttime switch beetween negative and positive value... This causes the "bouncing". But I don't understand the comment.

After further investigations it seems that it is these lines which causes the problem in BL_Action.cpp Update function: *Grab the start time here so we don't end up with a negative m_localtime when* suspending and resuming scenes. if (m_starttime < 0) m_starttime = curtime; Because m_starttime switch beetween negative and positive value... This causes the "bouncing". But I don't understand the comment.

Porteries Tristan commented

2015-10-28 15:11:10 +01:00

Changed status from 'Open' to: 'Resolved'

Porteries Tristan closed this issue

2015-10-28 15:11:10 +01:00

blender-admin commented

2015-10-28 15:13:12 +01:00

This issue was referenced by f10db730bc

This issue was referenced by f10db730bc4d8139e86ce078dd0fdd9fd07a8f35

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Action "Bouncing" when mixing automatic and manual action updates #45945