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DrQuincy
12-19-2003, 02:03 AM
Hello,

I am have rendered a greyscale image of my scene with just the volume light casting light onto black objects, plus I have a full colour render with no volume light. I am trying to composite the 2 together in Photoshop but have never done this before and just want to check that I am going about it the correct way.

I have added the lighting pass as a new layer on top of the full-colour render and then decreased the opacity and fill amounts until it looked satisfactory. Is this right or do I need to duplicate the lighting pass and use it as an opacity map for the lighting pass?

Many thanks. :cool:

Leovenous
12-19-2003, 06:55 AM
Somebody who knows what they are saying better than I do will probably say the same thing, but better. :)

Opacity is actually not a good way to go. Its simple, but you can lose detail, or just don't have all the control you ought to.

Layer modes. The little dropdown on your layers tab. Be default it says 'normal'. You need to change it to something like multiply, or screen or lighten... play with them and see what you get.

For a dramatic effect you may want to copy your lighting layer (Ctrl+a then Ctrl+c) then pull up your channels tab, make a new channel like you would a layer, and paste the lighting layer contents into it.

Then go back to your color layer (your normal layer), and run Filter>Render>lighting effects. Select a linear light and tweak it so it does not harshly effect your image. Then at the tab at the bottom you can select the channel you made, probably called aplha1 or something. Mess with the height and so fourth and accept it. The result should be interesting.

Anyway, solution no.1 is probably what you wanted. I'm sure even then you'll want to make some adjustments.

Hope that helps. :thumbsup:

Ian Jones
12-19-2003, 07:57 AM
Considering that you have two images, one containing all the colour and diffuse lighting and then you have a grayscale image of just the volume light... it sounds to me that you simply want to add the light from the volumetric pass to the diffuse pass with a blending mode such as 'screen'. This is probably the most ideal blending mode for your task as it will add the light in but not affect it with the black and dark tones of the volumetric pass.

DrQuincy
12-19-2003, 10:30 AM
Thank you both for your replies. Both were of help, thank you.

:thumbsup:

DrQuincy
12-19-2003, 03:54 PM
Originally posted by Ian Jones
Considering that you have two images, one containing all the colour and diffuse lighting and then you have a grayscale image of just the volume light... it sounds to me that you simply want to add the light from the volumetric pass to the diffuse pass with a blending mode such as 'screen'. This is probably the most ideal blending mode for your task as it will add the light in but not affect it with the black and dark tones of the volumetric pass.

Tried all the above and this one seemed to work out best. Thanks so much!!! Any other methods I should be aware of? (for still images only)

Cheers

Ian Jones
12-19-2003, 09:23 PM
The more you can understand about blending modes the easier it is to figure out what will work best. Check out the photoshop help for a description of each blending mode, you'll see why and how 'screen' works.

halo
12-20-2003, 01:16 AM
you may want to experiment with converting the spotlight to greyscale and using that as a mask as well (levels may need to be tweaked)

DrQuincy
12-20-2003, 07:42 AM
Originally posted by Ian Jones
The more you can understand about blending modes the easier it is to figure out what will work best. Check out the photoshop help for a description of each blending mode, you'll see why and how 'screen' works.

Yeah done! :) I can see why screen is often a good choice. Ok, now I know how it's done; I'm still struggling with the vlume light istelf. I'm currently using a volume spotlight in 3ds max, I'm after something like this ( http://www.cgnetworks.com/gallery/gallery_image.php?image_id=516 ) - do you think the rays of light here were done in a 3d modelling package or in PHotoshop?

Ian Jones
12-20-2003, 11:34 AM
I'm not entirely sure. In the thread the author says " its a 3D work, I used 3Ds max 4 default renderer, but worked after on the picture in photoshop". So maybe it was done in PS. Many ppl seem to have requested how he did it but it seems he never replied. I am guessing that it was probably done in ps. Unless you need animation, it can be easier and produce better results too. I really does depends though. If you plan on doing it entirely in ps, at least use the 3d voumelight as a reference.

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