Physical Light Effects Case Study

Bokeh in post?

2009-09-20T16:00:00.001-07:00

After waiting through the long render times of waiting for the mia bokeh lens shader I immediately sprung onto thinking of ways that might be used to separate a z-depth pass so Depth of Field could be manipulated in post in a more controlled and much faster environment.

Now doing this in maya to render as a pass appears to be impossible, just short of rendering a full Bokeh pass with Depth of Field and mixing that together with a Depth of Field controlled environment.... whew. Okay so in short, no quick 3D fix. If you want accuracy at that level you'll have to get tweaking or wait until somebody figures out a way.

How about faking it like how you can fake motion blur in 2D in post? Well why you can! Because the effect is closely tied with Depth of Field we can simulate the effect with a Z-Depth pass just like you would when you do to add depth of field in a controlled post environment.

after a bit of research you can do this manually however there are a couple plugins made for some post processing apps (alas you will have to shell out money or find a company/school to do so for you)

So far the most notable ones are the sapphire plugin and DoFPro

I've had the luck to use Sapphire for Nuke (OFX) and might be able to get a chance to see DoF pro in action soon.

Bokeh in Maya?

2009-09-20T15:18:00.001-07:00

Sure! In fact there's a lens shader made just for the occasion!

This is a copy of my first test in using the bokeh shader.

How do you go about doing this?

Simply using a new camera under the mental ray tab input a Mia_lens_bokeh shader

Now this is an effect calculated with Depth of Field through the mental ray renderer.

In order to show what is in focus we must input a value for the plane on which we want our focus drawn. To find this we can easily go into

Create > Measure Tools > Distance Tool

(Sorry for the lack of screenshot, but for reasons of not having a print screen button handy this will have to do.)

By placing your two locators at your camera shape and focal point you can calculate your plane input.

Now of course we'll naturally want to enable Bokeh, the whole point of this exercise. Just input your own Bokeh map.

The following are example of a couple Bokeh maps that you can use (click the photos to be linked to their origins)

What does this mean for us? Reaaaaaaly long render times. The test image at the top for a 1K image took approximately 30 minutes and with just the default 4 samples. Long but accurate! if tweaked properly a very nice effect can be achieved, especially with the sample rate cranked up. Be warned however, just like Lens flare this tool can be abused if used improperly, do keep note that strong bokeh appears with strong Depth of Field.

References

http://color-department.blogspot.com/2007/10/mialensbokeh-shader.html

http://ankitsharma.wordpress.com/2009/05/10/mia_lens_bokeh/

http://forums.cgsociety.org/showthread.php?f=87&t=803609&highlight=chromatic+abberation

Formed by the shape of our aperture you say?

2009-09-20T15:10:00.000-07:00

Why yes, The effect of Bokeh is directly influenced in a physical camera by it's apreture. What does that mean to us? it means we can make our own shaped apretures to make shapes in the lighted blurs of camera shots.

http://www.diyphotography.net/diy_create_your_own_bokeh

What is Bokeh?

2009-09-20T15:03:00.000-07:00

Bokeh

a term for a physical light effect spawned from the Japanese word for fuzzy

http://en.wikipedia.org/wiki/Bokeh

Well explained by Wikipedia in simple terms is a camera effect found by the shape of the aperture effecting the shape of blurred light as a result of Depth of Field.

All the little specs of light that blur into balls of light that you see in photographs are a result of this effect. Because of it's nature it is closely tied to the effect of Depth of field and Chromatic Aberration