Ghost People

[Matt McDonald]

On a particular project type I have been asked to show people as a nearly white matte. These people need to render essentially the same color in a night rendering and a day rendering. I am not able to tweak the material between the two because the people reside in a scene which is xref'd into my night and day files respectively.

 

I'm wondering if anyone has any suggestions as to how to do this.

[Peter M. Gruhn]

Self illumination.

[Matt McDonald]

Thanks Peter, I wish it were that simple. A material which has sufficient self illumination to render as nearly white in a scene lit by daylight is so bright in the night scene that there is horrible aliasing around the people in the night shot.

 

What we have come up with so far is to create a material that renders shadows but it's surface is invisible to the camera. We apply an MR named element shader to the material and then include the MR named element to the render elements. That then gives us a mask which, in photoshop we can fill with a semi-transparent white. This does the job ok, I guess.

 

What I would prefer is a material that does not self-shadow and can maintain a constant surface color regardless of exposure control. I don't think such a thing exists but if anyone has run across a third part shader that will do this, I'd love to try it out.

[erickdt]

I typically do my "ghost people" by doing a seperate pass using RPC people with everything else in the scene set to be matte objects (I use VRay). I then save the image with save alpha channel checked. You can then copy and paste the alpha channel from the rendering of the RPCs on top of you "beauty pass". Set layer style to screen with some transparency and you're all done. If you like you can ad in shadows and reflections as one would typically do with figures added in post.

 

Like I said I use VRay so this process might be a bit different in Mental Ray but I've gotta believe it's possible...

 

E

[Matt McDonald]

That's pretty similar to what we have settled on doing. It works fine but I'd love to get something that works with no post work. I think its probably a pipe dream though.

[Peter M. Gruhn]

oops. thanks for the update.

[MrCAD]

There is a solution with Ink and Paint Material to get the flat matte ..would easily work with mental ray and vray too

 

good luck

 

Meher

[postite]

Sorry I'm a bit late, but I made a similar project with matte people using Ink n Paint.

I assume you are using photographic exposure control.

 

First without transparency:

 

• create ink n paint material and apply
  
• choose your colour in "lighted"
  
• untick "shaded" and copy the lighted colour to shaded colour
  
• in the photo exp. control parameters, change Physical scale to unitless and value to 80 000
  

 

With transparency:

 

• create standard material
  
• Ambient & diffuse to white
  
• 2 sided
  
• Opacity 0
  

 

• create a blend material and drop the standard mat. and ink n paint into the two slots
  
• play with the mix amount
  

 

Here is a simple test made with that technique. Hope it helps.

[Matt McDonald]

Thanks guys, I'll give ink and paint a shot and let you know how it turns out.