Render Elements

[percydaman]

anyone with experience with conbustion, could they maybe explain how to use the new g buffer elements to composite all the elements into the image? Im trying out the combustion demo and have imported all these elements into it but am not sure how to make them all come together into the completed image.

[Seraph135]

What elements did you render out? Not all of them are necessary to put together the final image.

[percydaman]

ya I get that its not necessary to use them all but I grabbed them all. Im having issues with the refraction layer. The tga by itself looks fine, it shows all thats on the other side of the glass, but when imported into conbustion, everything behind the glass shows up as black.

It would be nice to know exactly what layers are necessary to recreate the final rgb image, so I know what I can adjust. Im a noob when working at compositing on this scale.

[Seraph135]

When you rendered your refraction pass...Did you make all other objects in the scene invisible to camera? You should. I'm putting together a little example. I'll post it soon.

I take that back...It depends on how your scene is getting rendered.

[percydaman]

no i didn't. I just wanted to see how the new elements worked so I just enabled all the g buffers and then rendered the scene. The vray buffer shows the proper refraction image in the buffer. And I think it transfers okay into photoshop, but im having tougher time with all the layers in photoshop 7.

Another thing, if I save the image into an rpf format, shouldn't all those buffers show up in combustion? I cant get it to work, but like I said, Im a complete noob in combustion and could just be making a mistake. Im not finding any GI related buffer images in the rpf format.

Oh and the z-depth buffer looks strange, some sort of yellow moire going on. I might have seen a post about that so Ill do a search.

[Seraph135]

It appears that in the current build the refraction pass does not get anti-aliased...

Photoshop 7 I don't believe has the ability to blend layers together "additively." I could be wrong though...I don't composite in photoshop

rpf's only save the information that is checked in the setup. GI is not included in that so you'll have to do those separately. Some of the other render elements that it does save like "object ID" or "material ID" are accessable, but you don't actually ever see those in your comp. When you add lets say a glow effect you will have options to use object id's or material id's to control where the glow will occur.

[cocolas]

I think in photoshop the closest blending mode that's adictive, although not purely adictive, is the "screen" blending mode.....but I could be wrong...I'm a noob as well to compositing

I did find this tute that uses Pshop as an example for comping.....

http://www.3drender.com/light/compositing/index.html

and here's his Pshop comping example w/ different blending modes...

http://www.3drender.com/light/compos...paceSample.psd


paul.

[vlado]

It appears that in the current build the refraction pass does not get anti-aliased...

It is antialiased, but with the original high-dynamic range colors; as you know, antialiasing doesn't work very well with HDR colors (e.g. the edges of a very bright light source - no matter how many samples per pixel you take, the edge is still going to be too bright); this is not specific to VRay but to rendering in general. For the normal RGB color channel, VRay uses clamped colors which is why you get better antialiasing on very bright parts of the image. For the other channels, VRay uses hdr colors. Probably something to think about in the future... there probably needs to be an option to clamp those as well.

Best regards,
Vlado

[vlado]

Another note: if you want to get the shadow alpha, similar to what you would get from a matte material, you should use (shadow)/(rawLight+shadow) instead of just the shadow channel. This will give you black where there is no shadow, and solid white in shadow areas. The shadow channel generated by VRay is simply the amount of light that was stopped by objects, and not the shadow alpha itself.

Best regards,
Vlado

[Gijs]

Cocolas: you can have additive in Photoshop as well, though not via the layers palette. You can do that with Image --> Calculations...
I think you are right though that Screen comes closest to pure additive. I found that using screen blending mode, your composite will come out slightly more washed out.

[percydaman]

ya thats what I found last night. I could come CLOSE to the original rgb image but not perfect in photoshop. Had less problems in combustion. Strange to me that photoshop after all this time is missing the tools to do it properly.

[cocolas]

@Gijs:
cool. I didn't know about the calculations blending modes...in there you mean the "add" mode, right?.......and yeah, you're right about the screen mode lookin a bit washed out.


paul.

[dans]

Photoshop HAS an additive blending mode. Straight from the psd-manager help file:

To composite render elements you often need an additive blending mode (e.g. for Specular, Reflection, Refraction, Self-Illumination). In compositing applications it is usually named Add, but in Photoshop 7 it is called Linear Dodge. In Photoshop versions prior 7 this mode is not available, there you should use the Screen blending mode instead (or use the Apply Image command where the Add mode is available).

Photoshop Elements 2.0 has the new blending mode too.

Daniel

[percydaman]

I tried the linear dodge, and it didn't seem to work well for me, but Ill check it out again.