How to define a background image?

[Michael ? flexiCAD.com]

Hi...,

how can I define a background bitmap in V-Ray? I don't understand it.

Please don't direct me to the manual, I haven't found it there. Or have I missed something?

Thanks,

Michael

[Coheed]

Re: How to define a background image?

if you are using the physical camera you need to increase the multiplier of your background image-start at 500.
you need to try.its try and error...
then you will see something.

[Micha_cg]

Re: How to define a background image?

... and "environment" should be set. Simple background images are not supported, only 360° panos.

[dalomar_cg]

Re: How to define a background image?

There is a distinct difference between "background" and "environment". A background is something that is just a backdrop to an image...this is something that is primarily for visual purposes (ie putting a rendering into an existing photo). An environment is something that is all encompassing...it surrounds the scene everywhere like a dome that is completely surrounding your scene.

V-Ray does the latter...uses images to completely cover that whole dome. One of the main reasons why is that backgrounds are not absolute and they are not complete...If you change the angle/location of the camera a background would stay the same relative to the camera, but not the scene. An environment would stay the same relative to the camera and not to the scene. As far as them not being complete...what kind of reflections would be traced for background images, since the image is only describing a small part of a whole environment?...maybe now you can start to see where a bit of the discrepancy lies.

Anyway, why am I going on this long winded explanation?...well just to let you know that even though Coheed's (love them by the way) and Micha's advice are correct, chances are they won't get you where you're really trying to go. What will?...Just adding that background in photoshop would probably be the most painless way of doing it. As long as you save your rendering in a format that uses an alpha channel (the only ones that don't are bmps and jpgs), then you should be able to put it in no problem.

[Travis Serio_cg]

Re: How to define a background image?

you could add a simple plane object and apply a planar map to the plane. This would be easy too.

[dalomar_cg]

Re: How to define a background image?

And in the sr beta set its alpha contribution to 0

[Travis Serio_cg]

Re: How to define a background image?

Damien, add this to the wish list for me. i already told joe, but i like when i can get multiple people buggin him muahaha

each objects alpha in the render gets saved to a separate layer in the png.

Might take some Vlado help, but that feature would make posting soooo sweet.

[dalomar_cg]

Re: How to define a background image?

Multiple people always have the tendency to get more things done...even if it multiple people bugging one person to do something ;D (we're a team, people, a team! ;D)...

Anyway, I would extend the wish to simply adding a few options when saving a specific image type...ie All types should have a "Save Channels as Separate Files" option, but jpgs should probably have a compression thing, pngs an option to save w/wo alpha, and maybe some other ones for HDRs/EXRs. Unfortunately though, something that extensive is probably not going to make it into the SR. But for formats that have the ability to retain the alpha information (pngs, tgas, exrs, hdrs) saving that extra file is a little annoying and takes up some hard drive space.

[Travis Serio_cg]

Re: How to define a background image?

png supports layers like psd's do. in fact png is probably more versatile than a psd. I just want it on a separate layer in the file to write a really tricked out compositor that allows our users to change stone color and metal color in a post process. I can do this provided that I have an objects alpha isolated on a separate layer

[dalomar_cg]

Re: How to define a background image?

TOL...The only way you could really do that within a png is if the only materials that generated an alpha were the gems themselves.

The thing about you're request is that you actually want Object or Material ID channel. that will allow for you to select the gem that had the diamond material as opposed to the metal band that held it. I'm not sure exactly what the deal with this one is, but I don't think that is some thing thats come up in any of my recent talks with Joe.

As far as pngs go, I looked up a little about them, and couldn't find any info that said that it supported layers (although it might be an old site (though it was the "official one")). It does have RGBA support meaning that its not alpha or nothing...I don't know if that rgb information is being written or not, but either way, the need for the alpha channel to be separate (ala targas) is much needed. Also, PNGs do have 16bit support as well as color space (gamma info) as well so those would be other cool options

[Micha_cg]

Re: How to define a background image?

The thing about you're request is that you actually want Object or Material ID channel. that will allow for you to select the gem that had the diamond material as opposed to the metal band that held it. I'm not sure exactly what the deal with this one is, but I don't think that is some thing thats come up in any of my recent talks with Joe.

This is at the top of my wishlist. My clients ask me often for that, because they want to adjust materials or create variants.

[Travis Serio_cg]

Re: How to define a background image?

TOL...The only way you could really do that within a png is if the only materials that generated an alpha were the gems themselves.

The thing about you're request is that you actually want Object or Material ID channel. that will allow for you to select the gem that had the diamond material as opposed to the metal band that held it. I'm not sure exactly what the deal with this one is, but I don't think that is some thing thats come up in any of my recent talks with Joe.

As far as pngs go, I looked up a little about them, and couldn't find any info that said that it supported layers (although it might be an old site (though it was the "official one")). It does have RGBA support meaning that its not alpha or nothing...I don't know if that rgb information is being written or not, but either way, the need for the alpha channel to be separate (ala targas) is much needed. Also, PNGs do have 16bit support as well as color space (gamma info) as well so those would be other cool options

Yeah I believe the site you are using is outdated. PNG is the work horse of the internet now. It supports layers, HTML slice info and all sorts of other neat goodies. All I need is each object UUID as the name of the layer, from there our compositor would be able to do post process effects like a crazy ninja as we would retain the original base material from the object and be able to translate in the png. We do some stuff of that nature with our 2d package.

[dalomar_cg]

Re: How to define a background image?

Although I think PNGs are great, I think stepping up to EXRs might just be a better route. A lot of that stuff is very well supported (I'm not sure how well supported it is in PNGs since I can't find the info), and its essentially the standard for compositing. One of the things about pngs is that it doesn't support 32 bit data, which can make a world of difference in compositing. Just my thoughts

BTW here's the website...maybe I didn't dig around enough, but it has been updated. Very recently I might add (jan14,0

http://www.libpng.org/pub/png/

[Travis Serio_cg]

Re: How to define a background image?

It appears that you can write extra info in the png to make it do whatever. I was curious after your post to find more info.

As a Fireworks user, i've been using png's for quite some time for web design. Fireworks is much better at web design layout than any traditional adobe product (I still consider it a macromedia product even though adobe bought them out. :-X ). I came across this info

http://www.adobe.com/support/firewor..._vs_sav02.html

[Travis Serio_cg]

Re: How to define a background image?

oh, png's can also support 8, 16, and 32bit data, but I agree with you about the Open EXR format. We need to look more into that.