Hi,
Been following this Optical Flow tut by Mark Fancher here: https://youtu.be/x2kMDuxd9J4 [youtu.be]

I noticed this intermittent blob appearing at the scene origin created by the fluid source node. Which in turn ends up emitting streams of particles throughout my final sequence.
Any ideas what could be causing this? is this normal?






Things I have explored are:
- checking the input img seq for stray pixels - its clean
- the next steps of adding velocity etc don't show any points at the origin, also checked geometry spreadsheet.
- tried tweaking fluid source settings but couldn't completely remove the blob, and changes affected the sim appearance
- Attempted to cull those particles by deleting white particles (that blob was causing white particles) but proved ineffective later on when I decreased particle separation for the final sim.

- On writing this, I notice Mark Fancher had uploaded his file. I tested with his network. It still shows a blob but doesn't emit particles from it. Comparing my nodes and settings, I can't find any differences.

Any help or pointers on what could be the cause is much appreciated!

Thanks
Tom

Hey Tom,

Nice catch!

This is indeed affecting my setup in the same way as you describe above, although it's not very apparent - likely due to the “centered” nature of the input I think I just assumed it was supposed to be there, haha.

After diving into the fluid source node and having a look at what it's actually doing, I've come to the realization that it's a bit unnecessary to have all that for this setup. So here's what I did instead:

1. Disable the Fluid Source node.
2. Replace with a point jitter node with the scale set to ~0.1 or whatever amount of randomness works for your setup.
3. In the following Attribute Transfer node, add “v” to the attributes listed under the points.

I hope this helps, and thanks for reaching out!
- Mark

Hi Mark

This worked a treat!

It gives a slightly different look, (better in my opinion) the way the fluid has more definition along the edges of my shapes.

I also added a Point Replicate node just to thicken out the source with more points. All is good now!

Thanks

Tom