# reflection in alpha **URL:** \ **Category:** Issues\ **Created:** [February 2, 2023, 5:39pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795 "2023-02-02T17:39:31Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 2, 2023, 5:39pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/1 "2023-02-02T17:39:31Z")
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](https://europe1.discourse-cdn.com/chaosprd/original/3X/9/8/989452fe1ffa1c80631ea71ef2149e40ada4f79b.jpeg) ---
**Author:** ![caypiranha](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/caypiranha/32/9482_2.png) [@caypiranha](https://forums.chaos.com/u/caypiranha)\ **Post date:** [February 2, 2023, 10:06pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/2 "2023-02-02T22:06:02Z")
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 =) ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 3, 2023, 1:05pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/3 "2023-02-03T13:05:36Z")
Yeah, this is how I achieve this. But I hope I can make it to work without render elements. ---
**Author:** ![Joelaff](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/joelaff/32/71647_2.png) [@Joelaff](https://forums.chaos.com/u/Joelaff)\ **Post date:** [February 4, 2023, 12:58am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/4 "2023-02-04T00:58:47Z")
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? ---
**Author:** ![vladimir\_krastev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/vladimir_krastev/32/42177_2.png) [@vladimir\_krastev](https://forums.chaos.com/u/vladimir_krastev)\ **Post date:** [February 6, 2023, 9:07am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/5 "2023-02-06T09:07:08Z")
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](https://europe1.discourse-cdn.com/chaosprd/original/3X/b/e/be203dbfb1aa443b5a3a742b057e97ae3a0bb6e8.jpeg) ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 6, 2023, 10:00am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/6 "2023-02-06T10:00:22Z")
> [@vladimir\_krastev](#): > > 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](https://europe1.discourse-cdn.com/chaosprd/original/3X/b/e/be203dbfb1aa443b5a3a742b057e97ae3a0bb6e8.jpeg) 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? ---
**Author:** ![vladimir\_krastev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/vladimir_krastev/32/42177_2.png) [@vladimir\_krastev](https://forums.chaos.com/u/vladimir_krastev)\ **Post date:** [February 7, 2023, 2:55pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/7 "2023-02-07T14:55:33Z")
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](https://europe1.discourse-cdn.com/chaosprd/original/2X/b/b1d9c56206546582e58917a5680649b966b414ed.gif) ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 8, 2023, 2:27pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/8 "2023-02-08T14:27:14Z")
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. ---
**Author:** ![vladimir\_krastev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/vladimir_krastev/32/42177_2.png) [@vladimir\_krastev](https://forums.chaos.com/u/vladimir_krastev)\ **Post date:** [February 8, 2023, 3:03pm UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/9 "2023-02-08T15:03:58Z")
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. ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 10, 2023, 8:14am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/10 "2023-02-10T08:14:02Z")
> [@vladimir\_krastev](#): > > 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. Yes, I know, there is no problem. I dont have bright areas in alpha at all. I will post some images. ---
**Author:** ![fixeighted](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/fixeighted/32/45854_2.png) [@fixeighted](https://forums.chaos.com/u/fixeighted)\ **Post date:** [February 10, 2023, 9:43am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/11 "2023-02-10T09:43:34Z")
Could you maybe cheat a bit by instancing the environment to the opacity channel? [EXAMPLE.rar](https://forums.chaos.com/uploads/short-url/6Bq45ywrrR6aT1VQM6OccsdSpof.rar) (245 KB) ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 12, 2023, 9:56am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/12 "2023-02-12T09:56:17Z")
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](https://europe1.discourse-cdn.com/chaosprd/original/3X/a/9/a942479baad218409b0f8a7103bcd88087e02d1c.jpeg) ![2.jpg](https://europe1.discourse-cdn.com/chaosprd/original/3X/9/3/93d4cb63ab20db3254675d79af4ca04e45bf4849.jpeg) ![3.jpg](https://europe1.discourse-cdn.com/chaosprd/original/3X/6/1/61dc2c8fe23bac6a9f9eca155183ee04776bc29a.jpeg) ---
**Author:** ![Jiri.Matys](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jiri.Matys](https://forums.chaos.com/u/Jiri.Matys)\ **Post date:** [February 12, 2023, 9:57am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/13 "2023-02-12T09:57:30Z")
> [@fixeighted](#): > > Could you maybe cheat a bit by instancing the environment to the opacity channel? Maybe, I can try that. But there are some options which should help in this situation. ---
**Author:** ![fixeighted](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/fixeighted/32/45854_2.png) [@fixeighted](https://forums.chaos.com/u/fixeighted)\ **Post date:** [February 12, 2023, 10:15am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/14 "2023-02-12T10:15:23Z")
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 😛 Anyway, maybe someone else will come up with an alternative… ---
**Author:** ![vladimir\_krastev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/vladimir_krastev/32/42177_2.png) [@vladimir\_krastev](https://forums.chaos.com/u/vladimir_krastev)\ **Post date:** [February 16, 2023, 9:50am UTC](https://forums.chaos.com/t/reflection-in-alpha/113795/15 "2023-02-16T09:50:37Z")
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](https://support.chaos.com/hc/en-us/requests/new) for uploading the scene. Please include a link to this thread.