Vray Sphere Fade alpha falloff problem

[smax]

Hello,

We have been using several times the Vray Sphere Fade to add new objects in our scenes.
It always remains a problem with the diffuse within the fading : it's colored grey (as set)

So it causes a little grey 'banding' that we can't remove (unless we post prod the alpha which sometimes isn't even possible due to images boundaries - i mean we can't contract the alpha when it's on the image limits)

Why does the RGB channel can't have the regular coloration of the scene while maintaining the same alpha (which would be perfect) ?

Also why do we see calculation in the glass (that look overall white) ?

Thank you very much

SMaX

[Sascha Selent]

Comp it with "Premultiplied with black"

Hi.
Set the empty color to black and do the compositing with "Premultiplied with black". Then everything is perfect (except te unwanted parts int the glass).

And don´t do it in Photoshop, it cannot do premultiplied compositing (correct me if I´m wrong). You have to use AE, Digital Fusion or Combustion.

...why do we see calculation in the glass? I don´t know...

[smax]

Thank you sascha,

It worked in premultiply.
(Now even the calculation in the glass fades a lot more with black)

Now not being able to use standard compositing (over premultiply) is a problem since i would like to dynamically "blend" this vraysphere fade with the original footage in flash for example (with let's say a .png file)

The only workaround i found is to render 2 jobs, one job A with a gizmo sphere of a given radius, and another job B with a radius divided by 2.
I then take the RGB channel of job A with the alpha of job B.

But that's a pretty long to set up, so i wonder if maybe Vray could generate regular images for regular compositing.

Thank you very much,

[vlado]

You should be able to do this with the data already provided by VRaySphereFade; it's only a matter of setting up the composition in your compositing application of choice.

Best regards,
Vlado

[smax]

Hello there,

I just found out out to fix my problem "cleanly".

I use png with "premultiplied matte" instead of "straight matte" and then i can compose the vrayspherefade directly in a photoshop or flash application.

Thank you again for this wonderful feature

[Sascha Selent]

Only one render necessary...

Now not being able to use standard compositing (over premultiply) is a problem since i would like to dynamically "blend" this vraysphere fade with the original footage in flash for example (with let's say a .png file)

The only workaround i found is to render 2 jobs, one job A with a gizmo sphere of a given radius, and another job B with a radius divided by 2.
I then take the RGB channel of job A with the alpha of job B.

Uh, no, much simpler: Take your original rendering and comp your gizmo-render as described with premultiply. Now you got a seamless comped full image with the new content in the old scene. Now you can just provide any new alpha channel you like with a mask - or take the alpha-channel from your gizmo-render. All done in comp. Only one render necessary (except the original rendering that´s already done).

[Sascha Selent]

Hello there,

I just found out out to fix my problem "cleanly".

I use png with "premultiplied matte" instead of "straight matte" and then i can compose the vrayspherefade directly in a photoshop or flash application.

Thank you again for this wonderful feature

Pardon me, where do you set this option? In Photoshop? In Flash?

[sv]

Pardon me, where do you set this option? In Photoshop? In Flash?

no in 3dsMax, (or a compositor)
The compositing options in Flash are absolutely 0; you've got to setup all the files before bringing them in, as you can't do anything to them in flash...it's so annoying!

[Sascha Selent]

I know about the poor compositing-features in Photoshop and Flash, but...

I use png with "premultiplied matte" instead of "straight matte"

Pardon me, where do you set this option? In Photoshop? In Flash?

no in 3dsMax

...where in max? In the PNG-settings there isn´t such an option.

smax, may you please describe the complete way you achieve your result now?

Thank you.

Sascha

[sv]

ah ok; now I come to think of it the instance I was thinking of we did the premultiplying in After Effects, then exported. I just assumed you could do this in 3dsMax also, but you are right with PNG's there isn't this option in the save dialogue....

[smax]

Yes, you are both right:
-There is not this option to premultiply black in save PNG dialog box in MAX.

So you can do it two options:
- in AE, combustion, reexporting the PNG with premultiplied
- or simpler (to me), in Photoshop : open all the files and do an action on the PNG:
Layer-> Matting-> Remove Black Matte (this assuming my premultiply color is black, of course)

I tested both, it outputs exact same image.

But i agree that having MAX (or Vray) outputing directly with premultiplied colors for the PNG would be nice.

Hope it helps,
SMaX

[Sascha Selent]

- or simpler (to me), in Photoshop : open all the files and do an action on the PNG:
Layer-> Matting-> Remove Black Matte (this assuming my premultiply color is black, of course)

Ah OK, I didn´t know this Photoshop-feature... Thanks.

[Sascha Selent]

Layer-> Matting-> Remove Black Matte (this assuming my premultiply color is black, of course)

I do not have this action. PS CS3. May you provide a screenshot? Is it self-done?

[RErender]

I do not have this action. PS CS3. May you provide a screenshot? Is it self-done?

it is in the "layer" menu, at the bottom

[Sascha Selent]

it is in the "layer" menu, at the bottom

Hm, I use a German Photoshop...