Render to elements transparency? (Vray 1.5)

[Xlars]

this is RC3, and it all appears to work fine here. I'm also using a fog bias of .22 like you, but this didn't kick up any problems...

[..]

I think the best thing to do at this stage, is just start with a clean scene, and set up another test material - sometimes strange things happen and a clean approach sometimes makes a difference.....

Thanks for your tests sv I forgot that I actully changed the fog bias. Good to know that this is not the problem. My investigation continues I think you are right about the clean scene - in this case it does seem to be narrowed down to the material giving me the problem (since I can get a new clean material to behave as expected).

[Xlars]

Thank you very much joconnell for your thoughts and explanations (I will read them over some more times for reference later).

In my case it is required that:

- Objects are transparent (but not glass as it would indicate from my test above). Objects have a very thin shell (shell modifier) so the background is not turned upside down or destorted that much.

- Objects needs to be placed onto already finished photographic background images. So I actually have no real 3d environment. Images are fixed ie. can not be changed in apperance or size. so I use them for background (screen mapped), lighting and reflection (spherical or cylendrical mapped) but also screen map them for the refraction override channel to appear correctly when seen through the transparent objects.

- I also need one or more of the objects as "generic objects" to be used for 2d compositing with Photoshop. This is where the Alpha channel would come in handy I thought. Have to work out some solution for that ... main problem now is that the (by the client accepted) material, similar to the one shown in my examples.. does not work for some reason. Will have to change the material to make it give me a Alpha or create a usable Alpha another way.

Thanks for your input - I will press on

[vlado]

Vlado - Looks like something odd with the fog/alpha in the alpha element, semi transparent alpha is rendering in the inverse color of the fog.

This is correct, yes. What is typically referred to as "alpha" is just the white complement of transparency. The alpha is actually a color, not a single floating-point value, as you can see for objects with colored transparency.

Best regards,
Vlado

[trixian]

Thought I'd mention that the affect alpha feature doesn't work for glossy refractions, and you seem to have used those on your first example.

[Xlars]

What is typically referred to as "alpha" is just the white complement of transparency. The alpha is actually a color, not a single floating-point value, as you can see for objects with colored transparency.

Best regards,
Vlado

Ah that is interesting, does that mean that when compostiting the "original" color of the objects "transparency" can be reproduced (using eg. some blending mode in Photoshop) ?

[Xlars]

Thought I'd mention that the affect alpha feature doesn't work for glossy refractions, and you seem to have used those on your first example.

Ah, I see.. is that the glossiness value you are refering to?

[trixian]

Thought I'd mention that the affect alpha feature doesn't work for glossy refractions, and you seem to have used those on your first example.

Ah, I see.. is that the glossiness value you are refering to?

of course