Photorealism Tricks of the Trade

Become a member of the CGSociety

Connect, Share, and Learn with our Large Growing CG Art Community. It's Free!

THREAD CLOSED
 
Thread Tools Display Modes
  03 March 2009
Photorealism Tricks of the Trade

Hey guys and gals. I thought this might be a cool thread to start. What are some of the tricks of photorealism in visual effects that you've learned over your studies? Here we can share this information. I'll list a few.

1. Using energy conserving, therefore physically correct shaders.
2. Linear Workflow
3. Not screening or adding fog/mist, but composite as an occluding element.
4. Setting motion blur to 0.5 or 50% to mimic the 180 degree shutter of a motion picture camera.
5. Adding grain, and other optical phenomena such as lightwrap, bloom, vignetting, lens distrotion, etc. to "imperfect" the final composite.

I know these are pretty basic, but some people miss them in their studies. Any other tips you guys and gals could throw out there would be appreciated.
__________________
Daniel Broadway 2013 Compositor Reel

Vimeo Videos
Daniel Broadway


Last edited by Daniel-B : 03 March 2009 at 04:04 AM.
 
  03 March 2009
*I am still learning like everyone here, so I dont want to sound like the "authority" on photo real, but here's is my 2c on the techniques i use in my own work:

For me it simply helps having an understanding of how things work in the real world. This can be a combination of visual analyses (eg staring a photo), and academic research(eg reading a paper how light works, and then working out how to apply it in 3d).

There is a big difference between realism(what we see with our eyes), and photo-realism(what a camera captures). I strive for photo-realism, it's the imperfections you get that generally make an image interesting(cg chromatic abrasion, lens distortion, film grain).

Couple things that i think help sell photo-realism:

- Correct light temperatures(eg sun is blue, tungsten(common studio lights) are orange ect).
- Depth of field, especially those funky bokeh hi-lights.
- Motion-blur (so many people seem to still skip over this)
- Proper physical Light fall offs
- Shaders that obey the laws of physics (i love mental rays mia for this).
- Always use SSS for skin
- Use physically correct lights (eg area lights)
- A good GI solution
- Where possible, render out everything in float (32 bit)
- Lens distortion
- Chromatic aberration
- Lens flares (i like stirring up a bit of controversy)
- Film grain
- Agree with above, adding lights blooms/flare in post can help heaps.
.... well thats a start at least!

edit: Read some further posts, and remembered some stuff:
> Black is never black, it's always slightly off
> The blue channel is almost always the grainiest when adding grain

Last edited by ndeboar : 03 March 2009 at 08:58 AM.
 
  03 March 2009
Working with a team of insanely talented people who know what they're doing.

__________________
leighvanderbyl.com
 
  03 March 2009
The best way to get your stuff photoreal is to get a photographic image in the appropriate format (ie the one you're trying to match) and really, really look hard at the thing to see what it is you're supposed to recreate and then work it out from there. Every format has its own idiosyncracies - there's no hard and fast formula for matching them - the only guarantee of success is diligent observation of the source. At the end of the day, everything you do in a VFX image is an approximate imitation of reality so creative judgement as to deciding what matters the most in selling a picture is just as (if not more) important than the technical route that you choose.

btw: rendering at reduced res and then interpolating up to soften the image is fine for low res formats like HDTV, but I wouldn't recommend it for film res work as it just introduces a whole bunch of additional filtering artefacts.

Originally Posted by PixelMagic: Hey guys and gals. I thought this might be a cool thread to start. What are some of the tricks of photorealism in visual effects that you've learned over your studies? Here we can share this information. I'll list a few.

1. Using energy conserving, therefore physically correct shaders.
2. Linear Workflow
3. Rendering CG at 75% final res to soften it in final composite through scaling, but also reducing render times.
4. Not screening or adding fog/mist, but composite as an occluding element.
5. Setting motion blur to 0.5 or 50% to mimic the 180 degree shutter of a motion picture camera.
6. Adding grain, and other optical phenomena such as lightwrap, bloom, vinetting, vignetting, lens distrotion, etc. to "imperfect" the final composite.

I know these are pretty basic, but some people miss them in their studies. Any other tips you guys and gals could throw out there would be appreciated.
 
  03 March 2009
Awesome thread!
Not long ago people here would of been up in arms over this thread.
Also be careful about mentioning chrommatic abrevation around here some people tend to think they are the authority on what effects can be used or not. j/k
 
  03 March 2009
You can also run your images through an unbiased renderer (indigo, maxwell, fryrender, busyray, sunflow etc) to get an idea of what the physically correct solution for your image is and then recreate that in whatever your actual renderer is.
__________________
"It's ten percent how you draw, and ninety percent what you draw" ~Andrew Loomis
 
  03 March 2009
Originally Posted by BigPixolin: Awesome thread!
Not long ago people here would of been up in arms over this thread.
Also be careful about mentioning chrommatic abrevation around here some people tend to think they are the authority on what effects can be used or not. j/k


also, it's chromatic aberration
__________________
"It's ten percent how you draw, and ninety percent what you draw" ~Andrew Loomis
 
  03 March 2009
Leigh's spot on, I learned a lot from working with matte painters. A couple of things really helped me out.

First was finding the right bits of reference. (flickr.com is your friend...) Sometimes it's good just for sussing out what the finish line is, sometimes it's awesome for generating textures. Not having good reference is like building a dog house without a blue print. It can be done, but with lots and lots of needless piddling.

The second thing they taught me was using data in image channels to cut out elements. Imagine you've got a picture of a tree with a blue sky behind it. If you look at the color channels, you'll find an almost perfect b&w image that'd make nearly a perfect cut-out of the tree. Then you use the dodge and burn tools to perfect the alpha and use it as a mask. Often that technique is not only faster, but more reliable in terms of getting a nice cut-out.

Fun stuff.
__________________
Maestro 2 is out!
 
  03 March 2009
cheat the audience eye for all cost! takes lots of shortcut
__________________
http://arifcreations.com/
 
  03 March 2009
Originally Posted by PixelMagic: 5. Setting motion blur to 0.5 or 50% to mimic the 180 degree shutter of a motion picture camera.


**I am interested in hearing more on this, or useful links on the subject.
I have just started rendering with 3d motion blur, and I left it at a default of 1, full 3d blur in mental ray, even though the moving object was going from the background to foreground.
It was a dark scene and looked ok to me, but would one normally adjust settings depending on the distance of the object from the camera?

I am concerned about having too much blur in my future scenes and how to determine the right setting.
 
  03 March 2009
Thanks for the comments thus far. Keep them coming.

Originally Posted by kelgy: **I am interested in hearing more on this, or useful links on the subject.
I have just started rendering with 3d motion blur, and I left it at a default of 1, full 3d blur in mental ray, even though the moving object was going from the background to foreground.
It was a dark scene and looked ok to me, but would one normally adjust settings depending on the distance of the object from the camera?

I am concerned about having too much blur in my future scenes and how to determine the right setting.


Motion blur in a motion picture camera is usually produced using a 180 shutter, and therefore producing "half" the motion blur of a full frame time. Since film is usually recorded at 24 frames per second, the resulting shutter speed of a 180 degree shutter is therefore 1/48th of a second.

Taking that into account, the proper motion blur setting in mental ray or other renderers to emulate this, is 0.5 or 50% motion blur. 1.0 or 100% motion blur is not realisitic in regards to film cameras, because the frame is advanced when the shutter is "closed" during the next 1/48th of a second. In other words, a 360 degree shutter or 1.0 motion blur is not possible, because there would be no time for the frame to advance.

EDIT: More useful info...

http://en.wikipedia.org/wiki/Shutter_angle
__________________
Daniel Broadway 2013 Compositor Reel

Vimeo Videos
Daniel Broadway


Last edited by Daniel-B : 03 March 2009 at 07:16 PM.
 
  03 March 2009
Ok cool.
I will try it out.
Maybe it will reduce my render time too(i hope!).
 
  03 March 2009
Hey Kelgy,

Motion blur in Mental Ray is a bit of a world pain (as in slow and noisy).

Nick
 
  03 March 2009
Originally Posted by ndeboar: Hey Kelgy,

Motion blur in Mental Ray is a bit of a world pain (as in slow and noisy).

Nick


**It took me 36 hours to render a 1000 frame animation with 3d motion blur.
But it was REALLY cool when I played it for the first time. It was my Jurassic Park test footage OMIGOD! Its got motion blur!!! moment.

edit: and its something I wanted to do since looking at adding motion blur in stop motion animation using vaseline on glass. I'd definitely something I'd rather leave to the computer.

I am re-rendering with the new settings and will compare the frames.

Last edited by kelgy : 03 March 2009 at 07:45 PM.
 
  03 March 2009
Add a photoshop lensflare
 
Thread Closed share thread



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
CGSociety
Society of Digital Artists
www.cgsociety.org

Powered by vBulletin
Copyright 2000 - 2006,
Jelsoft Enterprises Ltd.
Minimize Ads
Forum Jump
Miscellaneous

All times are GMT. The time now is 07:11 PM.


Powered by vBulletin
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.