Node Challenge

podperson

Well-known member
#21
The problem with Robert's approach -- which I agree is an inspired idea -- is that it blurs everything, including things that aren't glowing. It's essentially the same as simply blurring the render, only MUCH slower.

I think your best option is simply to render two passes -- one with just glows (everything else black) and then use that layer, blurred, as an additive layer on top of the base render (with everything EXCEPT the glows).

I think I've said this elsewhere but it's basically how glows are implemented in 3d renderers which do post-processing. It's how I'd do it in Blender.
 
#22
The problem with Robert's approach -- which I agree is an inspired idea -- is that it blurs everything, including things that aren't glowing. It's essentially the same as simply blurring the render, only MUCH slower.

I think your best option is simply to render two passes -- one with just glows (everything else black) and then use that layer, blurred, as an additive layer on top of the base render (with everything EXCEPT the glows).

I think I've said this elsewhere but it's basically how glows are implemented in 3d renderers which do post-processing. It's how I'd do it in Blender.
Well, I'm an absolute Cheetah beginner, but have a strong photographical background. What about using Robert's approach, but create something like a softfilter (http://www.bhphotovideo.com/c/buy/Soft-Effects-Pro-Mist/ci/117/N/4289364504), where defined areas stay clear and like a circular gradation it changes to mat?
Have to confess that I'm not (yet?) skilled enough to create something like that.
 
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#23
The problem with Robert's approach -- which I agree is an inspired idea -- is that it blurs everything, including things that aren't glowing. It's essentially the same as simply blurring the render, only MUCH slower.

I think your best option is simply to render two passes -- one with just glows (everything else black) and then use that layer, blurred, as an additive layer on top of the base render (with everything EXCEPT the glows).

I think I've said this elsewhere but it's basically how glows are implemented in 3d renderers which do post-processing. It's how I'd do it in Blender.
this *glare* thing andreu talks about is something i know very well from sometimes wearing dirty glasses. :smile:
so it's not about a blur filter, but about a *dirt* filter that distorts only a small fraction of the rays.
and it has to be combined with dof so that the dirt itself is not visible, only the glare distortion.
surprisingly it works, except for prohibitive rendertimes and the grain due to the way cheetah samples the dof.
of course this is no usable solution, which could be easily done in photoshop even on animations as it is not object but lens based.
but this challenge is not about a better solution but about finding new freaky, instructive and maybe elegant ways to utilize the new node system.
and robert has set me right on track with his idea. :smile:

What about using Robert's approach, but create something like a softfilter
umm, that's actually what i did, maybe the pic looks much worse than i think ...
 
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podperson

Well-known member
#25
Archie's blur is selective -- that's what I think he's saying. The problem is that even with the selective blur, the background (stuff behind the glowing object) is blurred as well as the image of the glowing object. You can see the brick bump pattern disappears around the glowing object. This may be acceptable, but it's (a) wrong, and (b) seems like at least as much trouble as the post method I proposed.
 
#26
Archie's blur is selective -- that's what I think he's saying. The problem is that even with the selective blur, the background (stuff behind the glowing object) is blurred as well as the image of the glowing object. You can see the brick bump pattern disappears around the glowing object. This may be acceptable, but it's (a) wrong, and (b) seems like at least as much trouble as the post method I proposed.
I slowly get it.... ;)

Thanks
 
#27
The problem is that even with the selective blur, the background (stuff behind the glowing object) is blurred as well as the image of the glowing object. You can see the brick bump pattern disappears around the glowing object.
that's not quite true, due to my lousy render (i tried a better one but crashed), the radiosity at 7 provides an overcast hiding all detail.
except from the very decent dof blur everything is sharp and the glare is just added around every bright spot.
that should become clear when i throw in a point light what i tried to avoid because it kills the neon glow.
also i show the index-of-refraction map in front of the main cam, you see black is more than 50% (when rendering it is 100x finer and 1 added to get refraction values between 1 and 2)

2.jpg

1.jpg
 
#28
Well I did an experiment last night and learned what Podperson was talking about. However, I had the whole plane blurred, instead of the focus area. Ideally, this should work if the blurring was reactive to light, which I believe is what Archie managed to do (I still don't know how :) ).

That said, I was also thinking about testing a convex lens (say fisheye) in front of the camera, with a soft "glass-like" mat on it. Be interesting to see how much of the scene you would get in at a certain resolution, than without it. Anyway, that's for another thread....
 
#29
Hi all!

It's been a while since I posted a node challenge. Never mind that, here we are again! :)

The next challenge has to do with volumetric glass, something that uses the an absorption amount to give glass that different color at different thickness.

Not too long ago, Martin was seen to say:


This effect can be quite easily implemented by an absorption term. Many renderer actually support this effect by an glass absorption property.

I haven't implemented it yet but it should be quite easy to support it in my new material system and it is on my 5.0 todo list. The CPU cost is almost zero.

Bye,
Martin
Anyway, while we wait for some future update, how about faking it in the meantime? This is the challenge: create or fake believable volumetric glass, or color absorption in glass on C3D.

Good luck!
 
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