compositing vraymat fog color and alpha

[khoross]

Hi guys

i have a project that require compositing a colored glass material ( by using a fog color in the material ) over a backplate .
not sure if im doing something wrong , while i have affect color and alpha in my material and getting the result i need in the vray frame buffer with the new backround image option .

the prob is when i same the image to png exr tga , cant seem to get the results . as in all image formats the alpha is greyscale .
should i composit all the element passes to get it right ?

example attached images

thank for your help

[khoross]

fixed the problem playing with translucency tx to this thread

http://forums.chaosgroup.com/showthr...t=translucency

[Svetlozar Draganov]

Hi guys

i have a project that require compositing a colored glass material ( by using a fog color in the material ) over a backplate .
not sure if im doing something wrong , while i have affect color and alpha in my material and getting the result i need in the vray frame buffer with the new backround image option .

the prob is when i same the image to png exr tga , cant seem to get the results . as in all image formats the alpha is greyscale .
should i composit all the element passes to get it right ?

example attached images

thank for your help
[ATTACH=CONFIG]23148[/ATTACH][ATTACH=CONFIG]23149[/ATTACH][ATTACH=CONFIG]23150[/ATTACH]

Would it be possible to attach that scene an explain us how to replicate the issue into our environment?

[khoross]

sure not sure if it's a vray issue though
here a few screenshot of my render & material.
trying to do an oil shader in a bottle , i set the fog color in vraymat to yellow & affect all channel, the results are great in VFB with background image on.
when i save the file & open in photoshop i get diffrent results with the same white bacground .





buoil-bottle.zip

[tsvetan.geshev]

Ok, you need to use the alpha channel as color filter in order to comp correctly the background and the final image.


For compositing you always need liner images, so the correct settings for Color mapping mode will be Color mapping only (no gamma)
Background should be black to avoid white fridging on the edges of the objects.
When you are affecting alpha channel you will get colored alpha /the color will be the inverted value of the diffuse of your material/
We recommend to to use 32bit EXR and to set you color profile in Photoshop to be sRGB

When you composite the image in photoshop:
- invert the alpha channel- this way you will get the yellow color
- multiply the inverted alpha by the background
- add your final image with plus operation to the background with already inverted alpha

[khoross]

thanks a lot it really helped me , i used to have the setting right in color mapping for compositing purpose,
i guess this time i did something wrong .
i wouldn't have never thought to composite it this way on my own ,
usually i use alpha just for background in architectural renderings, but i never came across colored glass and transparency .
many thanks