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Downsampling + Blur = Flickering part 2

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Hi guys,

after reading some advices from you, i got the blur quite smooth, but within animations, its flickering :(

Can someone give me an advice?



here is a video demo.

thank you very much

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From the effect it gives, I'd have a guess that you're using a fixed kernel size, which is then stepping over pixels and missing some data. As you gradually increase the size of the filter, you're "randomly" getting different pixels factored in, seen as a jitter. I'll try to explain what I mean in this image:

samplesa.png

That's not the best example I know, but hopefully will illustrate my point. As you move your sample points, you're getting different data coming in (under each arrow), and in the best case will interpolate between the nearest pixels. The fully blurred version of the above colour strip can "only" be obtained by sampling every pixel. The problem with using 3 samples is that (at most) you can only sample 6 out of those 9 pixels, which leads to a very different average, based on where the samples are taken.

Assuming this is the case, you'd be better to either increase your sample count/filter size when trying to get a more blurred image, or instead running multiple blur passes to blur the blur (taking averages of the averages!). Another option would be to look into downsampling the image and blending between the results, e.g. a full-size and half-size version.

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Thank you CukyDoh for your time, you could be a very good teacher! I was thinking now of increasing the sample size, but i thought that maybe i could get a bette result with biliniear filtering (actually i didn't use it till now, but read it)

28fig05.jpg

Am i understanding correct, that i am doing 4 lookups like this and get data of 16 pixels?: (middle point = actual pixel)

CCW:(top left beginning on orange dot)
(-0.5, -1.5)
(-1.5, +0.5)
( 0.5, 1.5)
( 1.5, -0.5)

I read it here: http://http.developer.nvidia.com/GPUGems3/gpugems3_ch28.html but i think they are doing it 6 times.

THank you for your time again.

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Am i understanding correct, that i am doing 4 lookups like this and get data of 16 pixels?: (middle point = actual pixel)


Yes, it should indeed! :)

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