Decimating a lot in one step vs decimating iteratively: which is best?

I was wondering whether there is a difference between decimating repeatedly at say 50%, or decimating at a much lower target percent, say 1%, in just one step? Is there a reason to think one method would give a better result than another. I’ve done tests decimating a smoothed box with 500k verts down to about 5k using both methods and I can’t detect any difference. Curious if there is any underlying reason in favour of one method or another.

Before 1.71 I would have said there isn’t a difference based off my usage. They both seemed to decimate the same. I would just use the 50% repeatedly so I didn’t have to try a certain percent, undo, adjust, try another percent, undo, adjust, etc. in order to get the decimation level I want.

However, 1.71 changed a little and using the 50% repeatedly didn’t work as well as before. So now I’m using the 1%.

Stephomi has it on his update list to fix/make better for next update and then I’ll probably return to the 50% method.

I saw that thread, and I think that’s what got me thinking about it. I tend to assume that iteration is best for most things, so it was interesting that in that case decimating all at once got better results. I wondered whether there might be a subtle benefit to decimating all at once in every case. I guess it’s probably worth trying both, as it might be quite specific to the geometry of each particular model.

Hey Jim, just as fyi -
Before, when using the 50% decimate repeatedly workflow, I would get small issues in the mesh. When taking it into another software to check for mistakes, I would have little errors here and there.

Decimating once at 1% and 1.5% (and I’d assume any other %) yielded a model without errors.

@RogerRoger it is specific to your model though.
Or rather models with very vertex small coordinates, but result should be normalised on next version.

I’ll run through a couple models and let you know what I find :+1:t3:

@stephomi Just to follow up- I’ve tested a few more models and yes or various sizes, decimating repeatedly does produce errors in the mesh. It’s typically not a hard issue to fix- just delete a few polygons and fill it back in but there are multiple errors in the same model.

Not a big deal. Looking forward to the release and will test it again there :slight_smile: