(EmberGen): Inconsistent Motion Vector Information for Weak Flames

I created a looping fire with a vector flow map for my game, but I noticed that the edges and tips of the fire appeared “steppy,” particularly near the top where the flames fade. This issue is most noticeable in the less intense, faded areas, while the hotter, denser parts of the fire appear correct.
brokenfireunity

I was able to trace the issue back to the vector map.

Here’s a comparison of one of the frame’s in the flame:
MotionVectorWrong
As you can see the less intense areas of the flame on the albedo, on the vector map are very faded and thus moving the flame a less and incorrect amount.

To confirm the issue, I created two new flames with no turbulence for clarity. I also reduced both the inner and outer blur on the vector map to help highlight the problem.

Weak flame with less fuel:
FlameWeakVectormap
Strong flame with more fuel:
FlameStrongVectormap

As shown, the vector map for the weak flame is faded, resulting in incorrect and inconsistent motion vector data compared to the rest of the fire.

Hey thanks for reaching out about this issue, and great work in putting this together. I am going to send this to the team and create an issue for it so that we can look into this and correct it while we do some bug fixing in the near future. If you run into any other issues please let us know, thanks again for the great post!