**System Information**
Operating system: Win 10 Pro
Graphics card: GTX 1080
**Blender Version**
Broken: v2.81, master, 2018-11-26
Worked: (optional)
---
**EDIT** by @EAW
**Short description of error**
> In the .blend file setup, the 'mesh_cache' object would instance a cube over the vertices for display in rendering. An ocean modifier is added to the object with 'Geometry' set to Displace and the 'time' parameter is keyframed over a frame range.
>
> Playback in the viewport shows the ocean modifier evolving shape during the animation. If the animation is rendered, the ocean modifier does not evolve over time and the render result is static.
>
> Here is a script that generates a 2d grid of vertices in the frame_change_post handler:
>
> ```
> import bpy
>
> def frame_change_post(scene, depsgraph):
> # Generate a 2d grid of vertices. A cube object is set to be instanced over the vertices for rendering
> vertices = []
> for j in range(100):
> for i in range(100):
> vertices.append((i * 0.05, j * 0.05, 0.0))
>
> mesh_cache_object = bpy.data.objects.get("mesh_cache")
> mesh_cache_object.data.clear_geometry()
> mesh_cache_object.data.from_pydata(vertices, [], [])
>
> depsgraph.update()
>
>
> bpy.app.handlers.frame_change_post.append(frame_change_post)
> ```
>
**Exact steps for others to reproduce the error**
> Here is the .blend file including the script: {F8175418}
>
> How to reproduce:
> 1. Open .blend file
> 2. Press 'Run Script'
> 3. Blender > Render > Render Animation
>
> The result is a static animation.
**End Edit**
---
**Short description of error**
I have created a FlipFluids simulation in Blender 2.81 ( 2019-11-25 21:45) and added an Ocean modifier in displacement mode to the fluid_surface. Then I have baked the complete sim from within FlipFluids.
When I move from keyframe to keyframe in the default timeline everything is moving as desired in the default 3D window:
Ocean modifier waves, FlipFluids waves & wake, flags, radars...
When I render the complete animation everything EXCEPT the ocean modifier waves are moving. The ocean modifier waves remain static but the FLIPFLUIDS waves move on that surface.
ALL modifiers and elements ARE enabled for renderings. D-NOISE: AI Denoiser is on (switching denoiser off did not help).
Computer is a HP Z800 with dual Xeons, 72 GB of vRAM and a GTX 1060.
If I render & save the keyframes manually individually by hand the ocean surface moves! Which means I get the proper result.
As its working when rendering&saving each frame manually as image (Png) and its not giving the same result when saving out the same images (Png) when I hit render animation, I do suppose this might be a bug in 2.81.
Running indiviual frames via Renderpilot did not yield the proper result either. So I do suspect it might be that there is not enough time gap between saving the last frame and rendering the next. Or, something does not get purged properly.
For propriatary reasons I can not share the blend file.