Glass alpha channels

[PhilippeV8]

You're right.  It does only work with simple glass and all it retains is the reflection and the coloring.  Any kind of refraction is lost if you change the background.  Which is expected behaviour.

Would be nice tho if we could render to such a smart format that keeps refraction active in post.

[DriesV]

Okay, I just figured something out...

If you have objects in your scene with solid glass and you REALLY want the background to come through in Photoshop, then do this:

*Render with solid glass assigned to object
*Render with 'simple glass' assigned to object with alpha channel enabled (this will take into account the transparency of the glass)
*In Photoshop open both images and release layer mask from transparency (layer > layer mask)
*Copy both simple and solid glass layers with layer masks into one canvas
*Finally, copy the layer mask from the 'simple glass' layer to the layer mask of the 'solid glass' layer

That should sort of do it...

Dries

[PhilippeV8]

Sort off indeed ... because you still lose refraction ...
It'll always look different than if you re-render with the final background.

[number12]

Firstly a BIG THANK YOU to PhillippeV8 for taking the time to post up about this. Keyshot is pretty new to us (just trying the demo currently) so still discovering what it can and can't do. So far, VERY impressed.

In response to EvilMaul our clients include Dreamworks and many other MASSIVE clients and we DO isolate 3D models, integrate it into something else and it DOES still look real so in essence you are 100% incorrect. (I can only assume we are slightly at crossed wires with this) It is sometimes necessary to separate your 3D model from the background/HDRI maps as for us, they are a means to an end, to give a realistic finish NOT to be left as rendered.

Anyway, I suppose we all use this stuff for different things.

You're right.  It does only work with simple glass and all it retains is the reflection and the coloring.  Any kind of refraction is lost if you change the background.  Which is expected behaviour.

Would be nice tho if we could render to such a smart format that keeps refraction active in post.

Yup, totally agree. It would turn this software from being great into being an absolute KILLER software.

Thanks for all your input guys, appreciate your time on it even though we may disagree on certain aspects! 

[PhilippeV8]

Then there is the scientific question as to what it should show refracted ... is it the backplate, or does it show stuff from the HDRI ... cuz if it is the HDRI, even a smart file format would have to be VERY smart indeed ...

[KeyShot]

It would be possible to add an alpha channel for the solid glass, but it would just show what is right behind the glass not what you might see at an angle (due to refraction). As Marco (aka Evilmaul) said this would be wrong, but if there is a significant request for this then we can certainly add it.

[vrank]

I know I'm digging up a relatively old thread. I'd like to see such a feature. Or is there a different workaround than the green-screen technique (or the one posted here) that produces the same idea straight from Keyshot?

We have to a lot of renders, with varying context. Meaning the post-production will take a lot of manual labor.

[Wonderboy75]

Hi,

I am a 3dsmax and vray user but I also use Keyshot occasionally at work.

I would just like to mention that V-ray has a solution where you can choose in the material if you want refraction and reflections to affect alpha channel and even other renderpass channels.  Here you can see a tutorial where this is explained. http://www.workshop.mintviz.com/tutorials/vray-alpha-channel-for-transparent-objects/

I hope there will be a similar implementation in Keyshot (if this is allready possible, please let me know) . It can be very useful when compositing your images.

[DMerz III]

I know somewhere out there, BDesign is working on a workaround for this.

Super BDesign to the rescue any minute now.

[bdesign]

  Thanks, David. I'll see what I can do...but, that's a tough one

Eric