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View Full Version : LW 11.5 sample scenes - why so many AA sample passes?



DonJMyers
02-02-2013, 05:39 PM
The new content for 11.5 is great both as examples and as "re-useable" bknd image probes and textures.

But why do so many scenes have huge numbers of antialiasing samples? Even the "inking demo" has up to fifty antialiasing samples for a line art image. Why so many?

I know these are "max samples" for use with "adaptive sampling" which restrains higher calculations to high detail areas where it does the most good. Does that mean you can have a bajillion passes but it won't use them all?

Why not just say "10 passes" and leave it at that?

Yours truly,

Passing out over passes

Jim M
02-03-2013, 02:45 PM
Concur

Celshader
02-03-2013, 03:06 PM
I know these are "max samples" for use with "adaptive sampling" which restrains higher calculations to high detail areas where it does the most good. Does that mean you can have a bajillion passes but it won't use them all?

Correct. The Maximum Samples sets a ceiling. It does not actually force the render engine to fire that many samples per-pixel. Maximum Samples defines a limit that cuts off the render engine after that limit is met. We did not have a "Maximum Samples" option in LightWave 9.2-10.1, which meant that the render engine could fire up to thousands of samples in a futile attempt to clean up a stubborn pair of high-contrast pixels. With that in mind, think of the LightWave 11.0-11.5 Maximum Samples option as a "safety" feature.

In Inking_Demo.lws, the Minimum Samples is set to 5 while the Maximum Samples is set to 50. This guarantees that all pixels will get a minimum of five samples, but whether or not a pixel hits the Maximum of 50 samples depends on that specific pixel. If you leave the Preview enabled in the General tab of the Render Globals panel, you can see this for yourself. Hit F9 and watch the render in-progress. The large areas of flat color stop rendering after the first pass of five samples. Only the high-contrast areas get highlighted in white, indicating that additional rays above the initial five samples are being fired.

For further proof that not all pixels are getting 50 samples, try a render that changes the Minimum Samples from 5 to 50. This will force every single pixel to start with 50 camera samples. On my machine, this Inking_Demo.lws takes twice as long to render when the Minimum and Maximum samples are both set to 50.

Dave Jerrard
02-03-2013, 07:08 PM
But why do so many scenes have huge numbers of antialiasing samples? Even the "inking demo" has up to fifty antialiasing samples for a line art image. Why so many?
To understand this fully, I refer you to this post:
http://forums.newtek.com/showthread.php?133294-Adaptive-Sampling-Info-Old-And-New

The high numbers may seem crazy at first, especially when compared to how the Classic Camera does things, but when you consider that generally, it's not EVERY pixel that gets this treatment, it's not so bad. In fact, many images render faster this way and look better than they did the old way. Generally, though, you still want to keep the maximum number of samples low. Most of my renders peak at 48, which is what LW 9.6 would give with an AA of 3 and a threshold of 0.03. That worked well for the majority of my work over the years. Only when things were still too noisy did I lower the threshold to 0.02 or, more rarely, 0.01, which resulted in 96 or 192 maximum samples.



I know these are "max samples" for use with "adaptive sampling" which restrains higher calculations to high detail areas where it does the most good. Does that mean you can have a bajillion passes but it won't use them all?
Yes. I've done that. Just because I could. I've also done that with the Minimum Samples. I don't recommend that though.



Why not just say "10 passes" and leave it at that?

That was one method I asked for a long time ago - to be able to say how many passes (which would, at the time, double the samples on each pass), along with an option to say how many additional samples are used (which we have now), and a mixture of the two; the number of passes and how many samples per pass. I still want these.

In 9.2-10.1, each pass would double the samples, so after the first few passes, each additional would start taking a lot longer as they got into the thousands of samples. 10 passes this way would mean at least 1024 samples with an AA of 1. Just look down the 10 Passes column in this chart (http://forums.newtek.com/showthread.php?133294-Adaptive-Sampling-Info-Old-And-New&p=1298054&viewfull=1#post1298054).

In 11, you can do this. Just enter 10 in the Maximum Samples and turn on Adaptive Sampling. Or, render without Adaptive Sampling and use 10 for the Minimum Samples. Or set everything to 1 and set the Motion Blur Passes to 10. The Adaptive Sampling version would probably render a bit faster though.



He Who Hates Misspelling Sampling As Smapling.

OnlineRender
02-03-2013, 07:18 PM
ULTIMATE LIGHTWAVE TAG TEAM! "commence"

DonJMyers
02-03-2013, 08:09 PM
Thanks so much folks! Dave Jerrard, you've got balls!

Chrusion
02-05-2013, 12:22 PM
If I recall correctly, LW 9 and earlier used an AA method whereby each additional "pass" thru the threshold detector doubled the number of samples. So if you started with an AA level of 4, the first AA threshold pass upped that to 8 samples/pixel, the second pass 16, the third 32, etc. In this way you could set the threshold value so that it "divided" the render into a desired number of passes, no matter how complex the scene. The new LW 10 and later AA system now just adds one extra sample to the initial minimum value for each "pass" until the max value of samples is reached, instead of logarithmically multiplying the samples. In this case, the maximum value determines the number of passes thru the threshold detector, but without the doubling of samples each pass, rendering is in most instances lightening fast as only one additional sample is added each pass at the expense of AA quality. That is, a few added samples such as going from an initial min of 4 to a max of 16, isn't going to smooth out aliased edges very much. It would be akin to the old LW 9 setting of 4 with a threshold of .1 or so resulting in only 2 AA passes (8 and 16 samples).

Dave Jerrard
02-05-2013, 11:11 PM
If I recall correctly, LW 9 and earlier used an AA method whereby each additional "pass" thru the threshold detector doubled the number of samples. So if you started with an AA level of 4, the first AA threshold pass upped that to 8 samples/pixel, the second pass 16, the third 32, etc. In this way you could set the threshold value so that it "divided" the render into a desired number of passes, no matter how complex the scene.


Before LW 9.2, we only had the Classic Camera, and a list of preset AA levels. In LW1 & 2, those levels were Low, Medium and Antialiased, but were actually resolution levels. In LightWave 3 to 4, there were Low, Medium and High AA levels, which actually corresponded to 5, 9 and 17 passes. LightWave 5 added enhanced modes, and 6.0 added Extreme, which was 33 passes. PLD modes were added in 8.2, which added several more levels of AA, up to 35 passes. In all of these modes (except for LW 1 & 2), Adaptive Sampling did a single check after the first pass to decide which pixels would benefit from all the additional passes, which made it evil for rendering fine details. In all cases, only one sample per pixel was rendered on any pass.

9.2 added the new cameras and the much better AA and Adaptive Sampling. The number of passes was always determined by the AA and threshold combination. The results are posted here for AA levels from 1 to 50, and for thresholds as low as 0.0001 (http://forums.newtek.com/showthread.php?133294-Adaptive-Sampling-Info-Old-And-New&p=1298054&viewfull=1#post1298054). This method was still in use in 10.1. You can also use Motion Blur Passes in 9.2 and up to define exactly how many passes are rendered, but this means that every pixel will be re-rendered on every pass.


The new LW 10 and later AA system now just adds one extra sample to the initial minimum value for each "pass" until the max value of samples is reached, instead of logarithmically multiplying the samples.I think you mean 11.0. 10.1 still doubles the samples like 9.2. No real changes were made to the AA until 11.0.


He Who Has Been Using LightWave For Half His Life Now.