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Justin Dewitt
New member
Username: Jimminy

Post Number: 3
Registered: 02-2007
Posted on Tuesday, February 06, 2007 - 01:40 pm:   Edit Post Print Post

Is there a way to get the 'background' material to NOT effect the alpha channel? I want to get it so an object set to 'background' will obscure other objects, but in all other ways (especially as concerns the alpha channel) be invisible.

I want to be able to render a normal scene without people or trees, then go back and render the people and trees, some of which will be obscured by the objects from the first render now set to 'background', and composite in photoshop by selecting the alpha channel in the people and trees rendering and deleting it to make everything but the people & trees transparent. Man, that's hard to explain.

If that isn't clear, I can upload examples, but the objective is simply to composite without having to manually erase things from the second render that would be blocked by things from the first. Being able to take advantage of the alpha channel this way would be really nice, but as it stands, the background material is just like any other material in the way formz deals with the alpha.

On the other hand, maybe someone here has a better method altogether they can share with me.
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Jean-Luc DAUREIL
Advanced Member
Username: Jean_luc

Post Number: 110
Registered: 07-2001


Posted on Tuesday, February 06, 2007 - 01:53 pm:   Edit Post Print Post

Justin,
have you a little picture to illustrate this?
jL
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Justin Dewitt
New member
Username: Jimminy

Post Number: 4
Registered: 02-2007
Posted on Tuesday, February 06, 2007 - 07:18 pm:   Edit Post Print Post

I'll have to try to find the time later.

The real issue is simply that I want to use RPC objects but they don't work with Maxwell, so I was going to try to do the rendering of everything but the RPC stuff in Maxwell, render the RPC objects in FormZ, then put them together using alpha channels to mask the RPCs that are obscured by other objects.

If the RPCs were always in the background or always in the foreground it would be simple, its when you have RPCs all over the place, and seen through semitransparent objects that you have trouble.

Maybe I'll just have to wait for that capability to be added to Maxwell.
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Jason Brown
Member
Username: Valkama

Post Number: 52
Registered: 08-2006


Posted on Tuesday, February 06, 2007 - 07:43 pm:   Edit Post Print Post

Hello

Try assigning a surface material, i use light blue with a constant reflection to all your objects except rpc content. Then in photoshop you can select by color and get rid of all the blue. Paste it back into your maxwell image and it should work. Whould be interseted to see the results if you try this.

thanks

jason
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Justin Dewitt
New member
Username: Jimminy

Post Number: 5
Registered: 02-2007
Posted on Wednesday, February 07, 2007 - 01:03 pm:   Edit Post Print Post

Yeah, that's the 'green screen' method, and works to a degree, but it falls apart when you have things that are semi-transparent or aliased because the color or value of the semitransparency effectively 'colors' the green screen making it not only difficult to select and remove those areas, but messes up the effect.
This is why an alpha channel is so effective. White is opaque and black transparent and all the values in between represent gradient levels of opacity. So, unless there's a way to convert the level of green or blue or whatever color you use to an alpha map, I don't think this will work.

The first image illustrates what I ultimately want after compositing. The second one is what you get when you set the objects to 'background'. The third is the aplpha channel for the second. If the third didn't show the boxes, just the alpha for the tree and greyed out where the tree passes behind the semi-trans green box, you would have it. Honestly, I can't think of a scenario when you would want the 'background' objects to show up in the alpha channel at all, I think this is an oversight.

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support@formZ.com
Moderator
Username: Tech

Post Number: 1534
Registered: 04-2001


Posted on Wednesday, February 07, 2007 - 01:43 pm:   Edit Post Print Post

Justin,

The Transparency of Glass Reflections are not included in the Alpha Channel because of the Refraction. But if you use a Simple Transparency instead (set Reflection to None) then you will get a partial alpha channel based on how transparent the object is.

Background objects should probably not affect the Alpha Channel (other than to exclude other objects from it) so we will add a suggestion to change this. Thanks for bringing this to our attention.

ZWebTech Support
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Jean-Luc DAUREIL
Advanced Member
Username: Jean_luc

Post Number: 117
Registered: 07-2001


Posted on Wednesday, February 07, 2007 - 04:09 pm:   Edit Post Print Post

Justin,

If i undersand correctly the problem is with Maxwell.

I don't know if you have a very big number of RPCs in you scene.
Perhaps you can try to make your own Maxwell materials with these decals.

Render the RPC from a front view with an alpha channel.
Map a new shape with this image + alpha transparence.
(You shoud make the equivalent Maxwell material as well)
I think it could be possible to render the scene with Maxwell without problems.

Let us know if one solution or another work for you.

jL
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Martin Malinski
Junior Member
Username: Notagain_uk

Post Number: 47
Registered: 08-2006


Posted on Wednesday, February 07, 2007 - 06:35 pm:   Edit Post Print Post

Another option would be Archvision Composer...
Allows u to place 3d RPC content into your 2d images..operates as stand alone or photoshop plug-in...So u could use a combination of Maxwell render, alpha and composite rpc.

Martin
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Peder Lindbom
Advanced Member
Username: Peder

Post Number: 116
Registered: 04-2001


Posted on Thursday, February 08, 2007 - 02:17 am:   Edit Post Print Post

Or Informatix Piranesi! Also supports RPC.

My workflow is:
Export to Maxwell ->render
Export to Piranesi.
In Piranesi import Maxwell render and add people/trees etc and tweak the image.

Works great. Piranesi can adjust the cutouts to the correct scale when placing them. It can hide parts of cutouts behind geometry and has great 3d painting features!

Peder
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gary moad
New member
Username: Gone

Post Number: 22
Registered: 06-2003
Posted on Thursday, February 08, 2007 - 10:20 am:   Edit Post Print Post

i would like to voice support for such a thing as justin is requesting. even though i realize this suggestion has already been added to your list.

g.