Yep… most noticeable at the smaller when the shutter is still “opening”. The AA and softness can help but ultimately offsetting small amounts in time and space seem to be the only way to minimize it in action as “single button” style fixes.
It’s a shame that you can’t just change the frame rate in action. Like you set something up in 24 but render it in 240 so you can get 10x the frames per second just by changing a single parameter. The secret to making these thing continuous is simply having more substeps like @Sinan was saying with particles. Other possible fixes are stretching the entire action out and then time warping back or writing some eval functions for all of your animated axis on new ones, but if you don’t want any visible stepping the object needs to be moving so slowly that the shapes overlap in accumulation.
The hyper white values help tremendously but if you need more it some of the tricks above.
I had a chance to look at the setup now and I was able to get rid of the stepping for the most part. I changed your working space to acesCG and the action nodes color space to acesCG first.
Next in action, I changed the image you’re animating to having an additive blend mode and changed it’s transparency to 90%. Then I added 9 additional axis and parented the same axis and image that your master animation axis is parenting. Next I selected those new 9 axis, go into the animation window, hit the expression button and enter the following expression:
eval(axis1, frame - (SelectionOrder * .01))
This will reference your axis1’s animation and then evaluate at the current sample of the current frame offset in time by the number in which you selected each axis multiplied by .01. So effectively this will instance the original animation, but for each of the 9 instances, offset the animation in time by -.01 per each instance and from each instance (so -0.01 first instance, -0.02 second instance, -0.03 third instance so on and so forth). I changed your shutter duration to 4.5 as well. It didn’t need to be open as long once I added the extra instances.
This will make the stepping all but disappear by effectively increasing your final subsamples to 2000 by first subsampling the picture “in comp” an additional 9x before you even hit the accumulation buffer. It’s also computationally cheaper than adding AA and softness I found.
