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Droolz
03-31-2006, 10:29 PM
Does anyone have any hints as to how I might recreate reflection blur in After effects? I'm guessing it would be something like using a normals pass combined with some sort of blur that reads this sort of info data, but I'm stumped - I'm pretty new to compositing so any if anyone has any links or tips to help me start it would be much appreciated.

All the best,

Jules

Vympel
03-31-2006, 10:52 PM
Simple blur in a reflection pass?

Droolz
04-01-2006, 07:52 AM
Yes I realise that - I was after whether anyone had any idea for a more complicated workflow where aftereffects is passed some information regarding the surface direction and can therefore blur in the correct 'direction'. A uniform blur simply wouldn't look correct, if anyone has any ideas they would be much appreciated.

Mylenium
04-01-2006, 08:49 AM
Does anyone have any hints as to how I might recreate reflection blur in After effects? I'm guessing it would be something like using a normals pass combined with some sort of blur that reads this sort of info data, but I'm stumped - I'm pretty new to compositing so any if anyone has any links or tips to help me start it would be much appreciated.

All the best,

Jules

Nope. I don't think that this type of stuff would ever work as a post process. A standard normal map does not capture distances between objects and reflective surfaces, it is a mere incidence map capturing the angle between surfaces, lights and camera. I guess one could combine it with some sort of custom-made height/ depth/occlusion pass, but even then you'd still need to manually animate values over time to get coherent results. It may be a major pain (because it's slow), but the current way of using ray multi-sampling is the only way to get halfway correct soft reflections.

Mylenium

Droolz
04-01-2006, 12:43 PM
Thanks Mylenium,

I guess that's why I couldn't find anything on the net ;)....

Jules

jussing
04-01-2006, 02:03 PM
Exactly what is the shot?

I had a similar problem when blurring reflections in the water, where I wanted the reflection blurred, but keep the waves (meaning the variation in the reflection) sharp and crisp.

One solution to that was to render a seperate falloff pass, and use that to mask between a raytraced reflection (blurred in post) and a sky reflection.

Worked OK.

Cheers,
- Jonas

beenyweenies
04-01-2006, 09:28 PM
Does anyone have any hints as to how I might recreate reflection blur in After effects? I'm guessing it would be something like using a normals pass combined with some sort of blur that reads this sort of info data, but I'm stumped - I'm pretty new to compositing so any if anyone has any links or tips to help me start it would be much appreciated.

All the best,

Jules

Can you post us a still showing what exactly it is you're trying to do? There may be no need for complicated 3d workflows depending on what you're trying to do.

avinashlobo
04-02-2006, 09:02 AM
Was just going through this thread here - http://forums.cgsociety.org/showthread.php?t=252304&page=1&pp=15

Contains a pretty useful little plug for mental ray (courtesy francescaluce) whereby, when using reflection blur, you can independently specify the number of reflection samples used in the FG pass, or even bypass them altogether & compute the blur only in the render phase. It's quite fascinating stuff really & from the tests shown in the thread (courtesy dagon1978), the render times are dramatically reduced with almost no visible difference.

I haven't had a chance to give it a go myself, but am itching to run a few tests myself.

It's techically (physically) inaccurate, but with around 1/3 the render time, this should be a minor grievance depending on how much of a purist you are.

On a side note, please do post any decent results you might find while on your quest for 2D reflection blurring and how exactly you achieved it.

Droolz
04-02-2006, 09:05 PM
Hey Beenyweenies I can't post anything as this is all specualtive at the moment - I do a lot of 'photoreal' 3d, and I've got an upcoming project that will be a nightmare. I use turtle primarily (thanks avinashlobo, I've been following that thread too, but not really applicable because of the renderer :)) and I'm looking at workflows that could potentially speed up the daunting render times.
turtle 3 has some really neat and intiuative baking functionality in it so one of the options is to bake everything down to surface shaders (all GI, FG etc) then the scene will render out super quick (it's likely to only be camera moves, hence getting away with the baking. The only 'true' renders I'll need to do would be the reflection / refraction passes & a depth pass.
Next step of my thinking would be to render out various matte passes to act as masks for the various items that need to have reflection blur applied to them (as they're likely to have differing ammounts of blur) and recreate the reflection blur in post using a compound blur based on the depth pass, creating new masked layers for any material that requires a different amount of blurring.

Problems i forsee with this approach is that the compound blur will pay no heed to the actual shape of the geometry, which is why I was originally thinking about having some sort of normals or sampler info pass to record some sort of surface information, but I'm guessing you would need a specially written blur effect to make use of this?
I'm also thinking that the blurring will look a bit shitty on the edges of objects, as compound blur leaves no option to 'repeat edge pixels' which is what I would need. all in all it loks quite a lot like I'd need a custom blur effect reliant on both a depth pass and normals / sampler info type thing.

apologies if this is simply not really possible, like i said, new to compositing :).

Jules

Vympel
04-02-2006, 09:37 PM
what are you make to obtain this "depth" pass (compound blur is limited to grayscale maps)? You plan to use this pass a mask in Compound Blur , like in a DOF effect using Compound Blur??

Droolz
04-02-2006, 10:11 PM
Hey Vympel, not sure I unsderstand the question completely, but yes, the same prinicple as a faked DOF, just used to make sure the reflective blur is affected by the depth of the object (ie an object far away would have a blur radius that is less than an object that is close).
The actual depth pass is a custom shader that gives me a bit more control over the start and end points (and gives a better colour depth than the maya default).

j.

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