Basic Comping of a Vray render

[Dynedain]

I just found out what the problem is. When saving to EXR from Vray, you aren't actually saving a floating point image, you're saving an 8bit image. We either need the newer build that Vlado says fixes saving to EXR in Max8 (I'm on Max7 with the Splutterfish plugin) or using the Vrayimg to EXR converter that we have to request from Vlado.

[Dynedain]

In my situation, the Diffuse*RawGI matched GI and Diffuse*RawLighting matched Lighting. The problem was occuring when adding Lighting to GI. It happened both if I used the composited versions of these passes, or if I just used the GI and Lighting gbuffers.

[cpnichols]

Oh... ok... there is a problem I did not mention in the tutorial. When saving the EXR, use the raw pixel option. That should give you the full float unclamped color.

[Dynedain]

Oh... ok... there is a problem I did not mention in the tutorial. When saving the EXR, use the raw pixel option. That should give you the full float unclamped color.

That doesn't seem to be an option in Max7+splutterfish plugin. I assume its the same as using "RealPixel RGB Data" and "RealPiexel Float" which I did. But apparently Vray 1.47.03 can't write out to EXR properly:

http://www.chaosgroup.com/forum/phpB...t=13832#112802

In my case, using 16bit rpf at least gives me functionality... not full floating point data obviously though.[/quote]

[rpc212]

Here is my Combustion schematic:



So it is the Lighting and Global illumination added together. This result then has Reflection and Specular elements added.

And the result:



Very blown out compared to the Vray rendered result. Also the shadows also look screwed up.



What do you guys think is wrong?

[rpc212]

Try this

See if (RawGI * Diffuse) is the same as GI and that (RawLight * Diffuse) is the same as Lighting. Because it should be.

I am suspecting that is a problme with the way that combustion is reading the data and/or displaying it.

Yep, they are the same.

[Dynedain]

RPC - tripod won't let you host images for remote viewing like you've done... try imageshack

but based on your description, its exactly the same thing I was seeing... which comes down to not being able to save floatingpoint data into EXR from Vray

[cpnichols]

Try this

See if (RawGI * Diffuse) is the same as GI and that (RawLight * Diffuse) is the same as Lighting. Because it should be.

I am suspecting that is a problme with the way that combustion is reading the data and/or displaying it.

Yep, they are the same.

RPC... do you think you could send me the EXRs at some point? Not now since I am going on a week long tropical vacation for xmas. but after the new year maybe?

[rpc212]

Hopefully you guys can see the images now as I put them on imageshack. Thanks Dynedain didn't realise Tripod wouldn't do that. Sorry.

cpnichols I will send you the EXR files after the new year.

[Morbid Angel]

Ok guys, RPC212 you did and additive on raw light and raw gi over diffuse as opposed to multiplication as far as I can tell thats why your image is so blownout.
This technique indeed works well below are two images comped using chirses method.

Vray render:



Comped:



There are very minor differences i.e. reflection is a bit stronger and not antialiased as well, the color on the blue box is different some what. But over all images are identical.

[oconv]

Dynedain wrote:

I just found out what the problem is. When saving to EXR from Vray, you aren't actually saving a floating point image, you're saving an 8bit image.

are you sure about that? if you reload your saved exr into a bitmap slot in the mat editor, you can preview it by clicking setup in the exr file load dialog and adjust its exponent black/white point etc.
from there they look like hdr images, no matter if you save from max or vray framebuffer.

-oconv

[dlparisi]

There are very minor differences i.e. reflection is a bit stronger and not antialiased as well, the color on the blue box is different some what. But over all images are identical.

What did you comp these in?

[Morbid Angel]

dlparisi, I used after effects.

[Dynedain]

Here is my result:




Whether I used the GI and Lighting passes, or constructed it the way cpnichols did with RawGI * Diffuse and RawLighting * Diffuse, I got the same result: blowout when I added the two together. However, I found that if I used 16bit RPF instead of Float EXR, I had success and my composited rendering seems to match the Vray rendering perfectly. This is what leads me to believe that something is incompatible with my Vray + EXR setup. I'm on Max7, Vray 1.47.03 and using the Splutterfish EXR plugin. And Vlado has said that there are issue with saving true floating point data to EXR, something newer builds of Vray than what I have supposedly fix.

[oconv]

since the openexr image format seems to work well in nuke, i assume it's rather an issue how combustion deals with openexr.
maybe some LUT's are required.
any insight from experienced combustion users would be great.

-oconv