Simulating Bokeh

[Jeff Mottle]

I've got an animation where I'm going to need to simulate Bokeh with some foreground lights in a night shot. For DOF in the past I've been using Combustion, but I think it just applies a blur and does not really do Bokeh. I'm using Vray and I suspect that using rendererd DOF would properly simulate this, but obviously I don't have access to 2000 nodes to be able to actually do rendered DOF and get it done before 2007.

 

Anyone else know how to do this? Can Combustion do Bokeh?

[Crazy Homeless Guy]

for slow people like me.... http://www.kenrockwell.com/tech/bokeh.htm

[STRAT]

i think Brazil does bokeh, but i dunno about vray. is it really that important Jeff?

[IC]

There was an article on advanced lighting techniques in 3D World magazine about a year ago and I'm sure it listed the renderers/programs that could do bokeh.

 

I'm not at home but if any of you have your back copies to hand........

[Ernest Burden III]

for slow people like me....

 

Thanks, saved me asking 'what the heck is'

 

Jeff

 

Low-tech wins the day...texture map. Use a self-illuminated map centered on the light and track it to the camera. If you really want to get fancy have it mapped with an animation, so the light bloom changes or vibrates over time.

 

Simple, effective, renders just as fast as regular.

[opus13]

personally i'd stick with combustion.

 

if you dont have time to wait for a painfully slow render (the only way to get true bokeh), then its all about the post process. its not hte 'best' result, but it will payoff quite handsomely as compared to the alternative.

[Jeff Mottle]

i think Brazil does bokeh, but i dunno about vray. is it really that important Jeff?

Yup, it really important as this is for a TV commercial and it's a forground element for the shot.

[Jeff Mottle]

Thanks, saved me asking 'what the heck is'

 

Jeff

 

Low-tech wins the day...texture map. Use a self-illuminated map centered on the light and track it to the camera. If you really want to get fancy have it mapped with an animation, so the light bloom changes or vibrates over time.

 

Simple, effective, renders just as fast as regular.

Hmmm, not sure that will work. The shot has forground trees with white lights in them. The subject in focus is about 50-60 feet away. The shot has trees on either side of the frame and because it's a night shot the lens would be wide open and create a really narrow DOF. I'm messing about in Combustion now, but it's definetly not that impressive.

[Jeff Mottle]

Slightly off topic, but why must rendering applications have controls for DOF that have nothing to do with how an actual camera works? You should be able to simply set the lens type you are using, set the aperature and the focus point. None of this Center Bias, Rotation etc etc crap. Even Combustion is lame this way too.

[IC]

With LightWave you just set the aperture and the distance

[Christopher Nichols]

You may want to look into XDOF... it seems to be a really good (albeit 2D), dof lense effect plugin. It can do a lot of things that 3D lense effect struggle to do:

 

http://www.evs3d.com/xdof_intro.html

[Jeff Mottle]

You may want to look into XDOF... it seems to be a really good (albeit 2D), dof lense effect plugin. It can do a lot of things that 3D lense effect struggle to do:

 

http://www.evs3d.com/xdof_intro.html

NICE! Thanks Chris, I did not know they had released this for max as well. Have you tried it? How exactly does it work with Vray, or can it. They don't have a demo or a phone number.

[Jeff Mottle]

To answer my own question: http://vray.info/topics/t0050.asp

[Ernest Burden III]

I didn't realize you wanted to have the entire foreground de-focused---just that you wanted the lights to have a blurry halo.

 

The trouble with Zbuffer based blurring is it can only target pixels for a percentage of an effect based on an alphachannel map. When you see through a blurry foreground it becomes transparent and what you see beyond will still be in focus. How to do this in CG without the heavy math?

 

One fairly simple solution would be to render your foreground in one or two passes (layering front to back) with alphas so they can be blurred and overlayed onto the focused background. That way, you will keep that focus of partially obscurred stuff.

 

You say a nightshot--how much will this foreground stuff be seen, how much movement? You can do a map with the trees already blurred like I had suggested, like a matte painting with projected stuff beyond.

[Christopher Nichols]

Yeah Jeff... just be warned that forground defocus is what is hard to do with a 2D effect. It is much easier to do it with background defocus. Check out the gallery and see if there there is an image that has a good foreground defocus.

[Ernest Burden III]

As a tangent...

 

I recall there was a thread--possibly from the old Lightscape user forum--about how you COULD, in fact, re-focus a blurry photo, if you had a few basic facts to start with. It was mostly the stuff of research papers, but it completely trashed the conventional wisdom that motion blurred or out-of-focus images have lost information irrevocably.

[Ernest Burden III]

The trouble with Zbuffer based blurring is it can only target pixels for a percentage of an effect based on an alphachannel map. When you see through a blurry foreground it becomes transparent and what you see beyond will still be in focus. How to do this in CG...

 

Off the link from todays news item about the xDof filter for Lightwave amd Max---this image shows what i was talking about http://www.evasion3d.com/gfx/xdof/gallery/domino1.jpg

notice how the blurred foreground still alows the middleground stuff to be sharp. Wonderful image!

[Jeff Mottle]

Yeah in the end I bought XDof. Nice app.

[Ernest Burden III]

Yeah in the end I bought XDof. Nice app.

 

Did you use it for the rendering you were talking about? I would love to see your results!

 

Of course, I will not back off the suggestion of a foreground imagemap as a poor-man's solution. It would work.