Simulation baking stops progressing during frame

[rlguy]

System Information

Blender Version (including hash): 3.6.3, blender-v3.6-release, 2023-09-21 06:06, d3e6b08276ba
FLIP Fluids Version: A FLIP Fluid Simulation Tool for Blender (v1.7.1 Stable 25-JUL-2023)
Operating System: Windows-10-10.0.19045-SP0
CPU: 13th Gen Intel(R) Core(TM) i9-13900K
GFX: NVIDIA GeForce RTX 3070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 536.23
RAM: 32GB DDR5

Describe the bug

From a recent report, simulation baking randomly halts during a simulation in the middle of a frame. The simulator does not crash or end, and just stops progressing while CPU usage reduces to 1%.

From the Blender System Console window, the simulator halts at the Advect Velocity Field stage. On Windows, the console window can be opened with Blender > Window > Toggle System Console. Example output:

To Reproduce

This issue may be able to be reproduced in any simulation set up, but in the case of this report the simulation was run in the Fluid in an Invisible Box example file at 400 resolution.

Baking from the command line does not prevent this issue. This may be a rare issue that does not affect all systems.

If you are experiencing this issue, or a similar halting issue, please let us know by replying to this thread or letting us know at support[at]flipfluids.com.

[ghpkishore]

I have a glass of liquid which I am animating. I was able to simulate the flip fluids and saw that it was progressing in each frame using the auto load checkbox. However, after the end of my keyframe 48, the fluid stuck in the last key frame during the animation and I had to click on reload frames for it to sync with each frame.

The bug resolved after restarting blender. But it took some time to figure out what the problem was.

[rlguy]

Thanks for the info @ghpkishore. Just asking for clarification: were you able to move the timeline past frame 48 and load future simulation frames after a restart without continuing the simulation bake? Or did the simulator completely stop running starting after frame 48?

The Auto-load baked frames feature can sometimes stop progressing frames while the simulation continues to run in the background. Depending on the context in Blender, the addon may not be allowed to change timeline frames which stops new simulation frames being displayed.

[ghpkishore]

@rlguy I didnt have any future simulation frames. My entire frame count was till 48. What happened was that it stopped showing the animation from frame 1 to frame 47 and consistently showed only the animation of the latest frame, which was frame 48. So i went to frame 39 and clicked on reload frame and it loaded frame 39. However, now when I started playing the animation, it got stuck at frame 39. So for every frame, I had to click reload frame for it to work. This problem went away when i restarted blender.