Blender Fluid produces spikes in mesh

[regionfive]

Hi,

I am using Yoyoz Blender Exporter for exporting animated scenes to octane.
But when it comes to fluid mesh exports, it produces some errors in the fluid mesh.
Does anyone have an idea, what the reason for these errors might be? Blender/the exporter/octane import?
A re-export/render doesn´t solve the problem.
I added an example video.
http://youtu.be/CdRiqVuXPNE
as you see, the problems are only in some random frames.
is there anyone who has found the same problem?

i am using blender 2.61, octane 2.52. and the 1.12 export script. but i already had these issues in older versions.
hardware: 2x 590gtx + latest update.

Thank you!
René

[regionfive]

i haven´t testet whether this could be because of the relativly high mesh solution of the fluid (about 300) because it always takes a long time to bake.
and i see these issues only after rendering. within blender, everything looks fine...

[steveps3]

So if you render inside Blender then you do not get these spikes?

[regionfive]

funny thing you ask, i haven´t used the blender internal for a very long time ^^ i tryed that now. although material is applied to the
fluid, it renders the whole scene !exept! from the fluid. this is strange. i really don´t know why. however, cycles is rendering it exactly as it should. and there are no spikes.
but i really don´t want to use cycles, cause it is much slower and i set up the materials in octane, not in blender. I don´t have any intention to do that anyway, because octane produces
the best results in the shortest time.
I really don´t get this. any idea?
greets!

[yoyoz]

The plugin's code that exports geometry is just an improved version of the default obj export script (so it supports some objects that were not exported by the obj one at the time I first rewrote the blender plugin). However, I may not have applied fixes that Campbell might have done since last year and there may be some differences now.

It would be nice you can isolate a single bad frame and export it to obj using the built-in exporter from blender. If you get same result then I can talk with Campbell to see why this happens. If it appears that it is specific to my plugin I can probably fix it by applying changes that would have been made to the obj exporter into mine.

If you could share your scene (privately), I may start investigating...

Cheers,
Yoyoz

[aLeXXtoR]

Lionel, I confirm this bug. This happens with Campbell's Wavefront exporter too.
It seems like it can happen in any scene with simulated fluid.

[aLeXXtoR]

You know... the funniest thing is that Cycles produces the same spikes while rendering...
BTW you can't see this while just previewing render in Viewport - you need to render your scene.

[yoyoz]

If it also happen with cycles full renders then the issue is probably more complex than just an export bug...
I couldn't reproduce it so far. I'll try again and I will open a bug once I can submit a sample scene.

[regionfive]

I rebaked a low mesh resolution (100) and did an octane lowres render too. there are no spikes at all.
i only previewed cycles, i didn´t know there was a difference. alexxtor, do you see these spikes in the internal render too?
as i said, blender internal doesn´t render the fluid in my scene (know idea why that is).
great that you take it so serious yoyoz

cheers

[aLeXXtoR]

Lionel, here is my example file. I also uploaded first 30 frames of fluid cache (~150Mb) — I don't know what result will you get if you try simulate it yourself.
Try to render frame 8 for example.
Thank you!

regionfive, internal render doesn't produce this spikes. I "fixed" this bug once that way: I rendered sequence in Octane, then used rendered sequence as a video source in Blender compositing (nodes); from blender scene (internal render) I got alpha channel for my water, applied it to image sequence, added motion blur (taken data from scene rendered with internal render too) to masked result and comosed blurred liquid with final image. This trick worked for me, but, ofcourse it is not the way out - at that time I just had no time to write bug reports and wait for an answer - I needed work to be done very quick. ))