Pixel Filters

Started by reck, November 10, 2008, 03:12:14 PM

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reck

So has anyone got any useful information on the new Pixel filters? I know some of these filters are used in other 3d apps and i've seen their docs but i'm more interested in how they work in TG. For instance I know some are pretty basic, some offer sharper results while others softer but is there a general all round good filter to use in TG.

Maybe it's best to use one filter over another when developing certain scenes, but which filter should be used where?

Also has anyone got a grasp on how each of the filters affects rendering speed. I know box is the most basic filter but does it render a lot faster than say Mitch or Catmull? If not is there any point in box any more?

Right now when it comes to render a "final" output i'd be pretty much guessing which filter to use, some guidance would be handy if anyone can offer some.

Mohawk20

Once my current render with a rock object is complete I'll run a scene with definite hard edges through all the filters and post the result here with all the rendertimes.

It could take a while though, perhaps a day or 2...
Howgh!

reck

Nice Mohawk.

I've just done a quick test with a default scene and a sphere added. I rendered the same scene with each of the filters.

No filters - 0.34
1.10-Box-1.11
2.10-Tent-1.37
3.10-Narrow Cubic-1.36
4.10-Cubic B-Spline (soft)-3.28
5.10-Michell-Netravali-3.27
6.10-Catmull-Rom (sharp)-3.36

I think the scene was a bit to basic to get a good result but roughly speaking box is certainly the fastest with catmull the slowest. The ones in-between took roughly the same amount of time. In terms of quality it's hard to tell with this very basic scene. Box was the worst but there wasn't much in it with the others.

old_blaggard

I don't think that there's going to be any specific answers. In some of my scenes, I've actually decided to stick with Box because the others seemed to soften things a bit too much. It all depends on the context, though.
http://www.terragen.org - A great Terragen resource with models, contests, galleries, and forums.

dandelO

I like to use Catmull-Rom with AA bloom checked. This keeps everything really snappy but softens up really bright reflections/highlights beautifully with the bloom option.

Matt

Hi Reck,

What did you mean "No filters"? What is the difference between your settings for "No filters" and for Box? And I'm afraid I don't undestand what the first set of number (1.10, 2.10, 3.10 etc.) mean.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Matt

Some of the filters will add some time to the render, as will anti-aliasing bloom (but not necessarily additively, i.e. aa-bloom won't make as much difference to the render time with catmull-rom as it will with one of the simpler filters like box). But these time differences should tend to amortize on more complex renders, simply because more time is spent on the actual rendering.

Also, these filters will make more difference to render times with higher AA settings.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

reck

#7
Quote from: Matt on November 10, 2008, 11:32:59 PM
Hi Reck,

What did you mean "No filters"? What is the difference between your settings for "No filters" and for Box? And I'm afraid I don't undestand what the first set of number (1.10, 2.10, 3.10 etc.) mean.

Matt


By no filters I just mean i'm not using AA at all, the AA setting is set to 0.

The first number is just the order that they appear in the drop-down 1 for box down too 6 for Catmull. The 10 is the AA setting I used for the filter. Now you mention it it does look a bit cryptic. The numbers after the filter name is obviously the time to render.

Thanks for the useful info.

Mohawk20

#8
Okay, here are 6 renders, without AA bloom.

The times:
Box                          - 0:46:32
Tent                        - 0:47:42
Narrow Cubic             - 0:48:28
Narrow Cubic B-Spline - 0:48:56
Mitchell-Netravali       - 0:48:49
Catmull-Rom              - 0:48:31

I chose to render a simple scene the still takes a relatively long time, to see how the rendertime is affected. On 3 quarters of an hour, one or two minutes don't matter that much.

The differences in effect can clearly be seen, close up, but perhaps even more so in the distance.
Narrow Cubic B-Spline gives the smoothest results in this case.


Next post will have the same test with AA Bloom on.
Howgh!

Matt

#9
The fourth filter is just called "Cubic B-Spline". The word "narrow" is only included in the third filter to distinguish it from the cubic filters used by other renderers because the "Narrow Cubic" uses a smaller filter width than might be expected by someone who has worked with pixel filters. I don't mean to sound pedantic, but.. there we are.. :)
Just because milk is white doesn't mean that clouds are made of milk.

Matt

#10
These appear to have no anti-aliasing? Or the white stones are extremely bright?
Just because milk is white doesn't mean that clouds are made of milk.

Mohawk20

#11
Good to know...

On the other hand, I care more about the effect than about the name  ;)


The stones have an opacity of 0, and have a very bright light under them, so the scene tests the extreme.
The light comes from a 2nd planet that is 6.3779e+006 in size, while the planet with the fake stones is 6.378e+006. The smaler planet has a surface layer with a luminosity of 100.

Oh, and the AA strength is the default 3 in these renders.
Howgh!

Matt

If the hard aliasing is due to the white parts being very, very bright, then you will not be able to see most of the differences that these filters produce, and you are in the territory that anti-aliasing bloom is designed to handle (with the other filters not really being the important factor anymore).
Just because milk is white doesn't mean that clouds are made of milk.

Oshyan

Here are some earlier filter tests I did. Check file names for the filter types.

- Oshyan

Oshyan

Continued...

- Oshyan