reflection in alpha

V-Ray V-Ray for 3ds Max Issues
1

Hi,

I have object of door with glass in it. I need to render animation with alpha so background will be transparent. There is a reflection on a glass from dome light which looks nice and I want it remain. Problem is that I dont want glass in alpha (otherwise it will be black as background). What I need is transparent glass but reflection to be opaque in alpha. I thought this can be done with affect channels color+alpha in reflection of glass object, but nothing happen. How can I achieve this effect?

Thank you.

aa.jpg
aa.jpg201×357 29.1 KB

2

Hi,

then don’t put it in alpha. straight plain mask for the windows and set your BG behind. get a reflection/ specular renderelement and set “screen” - for instance - in compositing to archive the refl.

.. if I understand you right =)

3

Yeah, this is how I achieve this. But I hope I can make it to work without render elements.

4

Like effect of using a matte object with affect reflections enabled? (Either in the Vray properties or with a VRayMtlWrapper)

Does that do what you want?

5

Hi, thanks for posting. Won’t it work if you set your refraction to affect color+alpha?
Setting it up like this will remove the glass from alpha and keep the reflection.

3dsmax_2023-02-06_11-05-19.jpg
3dsmax_2023-02-06_11-05-19.jpg361×1014 102 KB

6

As I wrote in my main message I thought that too but its not working. Maybe bug? I dont know. Can you try it on some simple scene please?

7

Hi I did try it before I replied yesterday and it works. This is specular and it is a bit darker compared to the original without alpha (see the gif below).

Photoshop_2023-02-07_16-53-48.gif

8

Maybe because I have reflection from HDRI map dome light? Its in specular channel and not reflection. But it should still work I guess doesnt matter what light source is used.

9

If your glass is not fully transparent the alpha is not fully black. Depending on how strong the reflections are and what colour the new background is the reflection could become less visible or even hard to notice.

10

Yes, I know, there is no problem. I dont have bright areas in alpha at all. I will post some images.

11

Could you maybe cheat a bit by instancing the environment to the opacity channel?
EXAMPLE.rar (245 KB)

12

There are images. Reflection and refraction affect alpha but reflection is not there. When affect alpha only reflection not refraction, reflection is not there too.

1.jpg
1.jpg423×411 46.3 KB

2.jpg
2.jpg351×228 22.4 KB

3.jpg
3.jpg493×592 10.8 KB

13

Maybe, I can try that. But there are some options which should help in this situation.

14

Feels like there should be another option but I can’t see it tbh, as, like Vladimir said, if you only have the standard reflection and a totally clear alpha then any background will quite
substantially reduce the apparent reflection.

Honestly I wish I’d thought of it when I was doing a load of saunas a while ago that had the exact same issue that at the time I couldn’t figure out :stuck_out_tongue:

Anyway, maybe someone else will come up with an alternative…

15

Hi, if you’d like to please upload your scene. I will review it and we can discuss it here. Maybe there is something wrong in the end and I am unable to reproduce it.
You can also use the support contact form for uploading the scene. Please include a link to this thread.