topic Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View in Arnold for Maya Forum

Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Tue, 04 Sep 2018 09:53:50 GMT

UPDATE: Please read the post.. If LMB select a glass GEO I get the same Alpha Chanel Value like in the Maya Render View! Totally strange! Updatet Image below:

I found out that the Alpha Chanel is more opaque when you render with the Maya Render View Window. But when you render with the Arnold Render View Window everything looks correct.
I made a new test scene to try out.. I worked the hole time with the ARV and after submitting to the render Farm I can throw away 450 Frames.. So any Idea how to solve the next 450?alpha-issue.zip

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Tue, 04 Sep 2018 13:16:58 GMT

If the image rendered to file is different than what you see in the ARV, then I would look at color management, and what color transforms are being applied.

Is that the case? Rendered image not the same as the Arnold Render View?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Tue, 04 Sep 2018 15:18:50 GMT

Hello @Stephen Blair! Yes this is the case. I am Rendering inside Maya and getting this results. Rendering with the Arnold Render View looks right but rendering with the Maya Render View seems false. I just used the MRV to check my issue. I always render with ARV until I got this Issue.

I tried your suggestion about the Color Management and I got weired results. When I untick Color Management I get the same Alpha like in the ARV but then the colors are false... so no matter what and can´t get both renders equal..

I attached some images.. could you be so kind an try out my attached sample scene? I have my deadline in 5 Days.. and it is mostly impossible from now on to get done.. Nightshifts! 😄

Thank you very much!

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Tue, 04 Sep 2018 15:27:19 GMT

So here is my Case. I try to render this shelter and it has to be composited onto another image. So I really appreciate any solution..

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Tue, 04 Sep 2018 15:28:09 GMT

You wrote that you had to throw away the frames rendered on the render farm.

I rendered your scene to disk, and the image file alpha channel matched the alpha channel in the Arnold Render View.

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Tue, 04 Sep 2018 15:45:38 GMT

ARV applies an sRGB transform, so it won't necessarily match what you see in an external viewer...it depends on the viewer settings. For example, here I've switched the ARV view transform to Raw, so it matches what I see in my viewer.

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Tue, 04 Sep 2018 16:17:02 GMT

Hello @Stephen Blair, I understand what your´re saying. I think my problem is not in Gamma Correction. In my last Images above you see that the opaque Elements match (almost) the ARV. The metall Frame is a bit brighter because the glass is not fully transparent and scattering light > What is my Problem

All Glass Elements are washed out and do not have the Reflections/Refractions like they should. When I did compare the renders I see that the Alpha Chanels are different and therefore the Glass looks different.

I do not have Problems with all opaque Materials, just with transmission and TRANSMIT AOVs Function. I need the transparent Alpha for Glass for comping them onto other Images.

So any Idea what my render Problem is? When I save the Beauty and AOVs (Single or Multi_EXR) everything is fine in my image viewers/Comp Software.. but I can´t render 450 Images by Hand! 😄

So I really like to think that I´m doing something wrong.. but I see no reason why my ARV Render looks different then my farm render. In my color Checker Images above you see that my Color Management does work properly. Neutral Grey 128 in the source File is Grey 128 in my batch render.

So I think there is a bug in the TRASNMIT AOVs Setting, because I do not have that Problem when I uncheck that Function. But without I can´t render for Comp.

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Tue, 04 Sep 2018 17:52:19 GMT

Your batch render looks like a texture might be missing. But I can't really tell from just a screenshot. Maybe if you had Arnold logs, that would be a start.

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Wed, 05 Sep 2018 10:53:26 GMT

Hello @Stephen Blair,

so I found the issue. I did render a local batch and I got the same results like you did. When I was looking at the Farm Renders I did see the washed out Alpha.. Then I did a test with the MRV locally and it did look exatcly like the Farm Render as you can see the differences with the test File above.. So the Maya Support did proove that too. Normaly they should look the same, since I use the same Color Management Settings in both render views..
Because I was submitting another case to the support where I don´t see aiMatteShadow through glass with Transmit AOVs ticked on, I thought this is another issue with transmission...

But I was dump.. I should test all pathes or common problems first, what I not did, because I got different results with the render view.. I thought when my ARV looks correct then there can´t be other issues.. and prooved myself by the MRV..

I´m not sure why but I did reconnect everything and after that it did work, both locally and on the farm..
But my apologies for making confusion..

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Wed, 05 Sep 2018 11:20:09 GMT

@Stephen Blair Is there maybe any solutuin for my other case? I tried to increase depth in the transmission tab, but somehow the aiMattteShadow does not cast shadow through glass. I apllied a standard surface and the shadows show up. But I need them with alpha. I did try out all AOVs but there is no one who shows Shadow through glass..

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Wed, 05 Sep 2018 19:25:37 GMT

Sorry, I don't understand what's going on in those screenshots. Why does the bench disappear when it's not behind glass? Why isn't the ground plane visible through the transmissive surface? Then bench is visible, how?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Thu, 06 Sep 2018 00:37:30 GMT

Hello @Stephen Blair,

Your question "Why isn't the ground plane visible through the transmissive surface?" is exactly my question. My goal is to render out the shelters shadow cast on the ground and seen through the glass Elements.
What you see here is just the Glass Elements "Primary Visibility" turned on to show that something is missing on my Ground Planes "aiMatteShadow".
The bench is seen through the glass because I did turn on "Transmit AOVS". Without this option the glas would render black on "background" pixels. I like to have transparent pixels for comp.

The bench is not seen outside the glass elements because its "Primary Visibility" is turned of.

So without touching this case:

Is it possible to render out shadows cast from an "aiMatteShadow" shader through glass when "Transmit AOVs" is checked on in the "transmission" tab? Or is it something for future releases?

Thank You very much!

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Mon, 10 Sep 2018 13:40:25 GMT

Ground plane with aiShadowMatte, and shadow is visible through two transmissive objects (with standard surface and Transmit AOVs enabled).

If you're not getting that, maybe you can post a simple scene that shows what you're doing?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Thu, 27 Sep 2018 15:33:58 GMT

Hello @Stephen Blair,
sorry for my late response.

Attached you find an Image and a test Scene. I try to get a clean shadow pass with proper refraction of the shadows because of Glass Elements infront of the camera.

I know it was kind of irritating, because of the wired Renderings in the last posts.. I tried with visibility options to just see the shadow pass without anything else. But no matter what I do I always have some sort of Glass Shading in my images.. I can´t separate them..

Is it possible to render a shadow pass where Glass Elements infront of the Camera properly refract the shadow, but the Glass itself is not visible?

shadow-catcher-test.zip

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Thu, 04 Oct 2018 18:12:10 GMT

Try disabling Primary Visibility on the glass geometry ?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Thu, 04 Oct 2018 18:44:27 GMT

I did try everything.. it seems that this is not supported in any way.. so maybe you could add that to a request list? Or do you have another solution?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

Stephen.Blair — Thu, 04 Oct 2018 19:25:15 GMT

So, not like this, but something else?

Re: Alpha Chanel is more opaque Maya Render View Window then in Arnold Render View

nicolasDE — Thu, 04 Oct 2018 20:44:55 GMT

So the right diagonal side looks correct. No Glass Element visible exept a shadow on the ground. Do you get proper refracted shadows as well? So with higher IOR and sharp shadows it should be more visible.
But I think I never had the combination of PV and Shadow Pass.. My main Problem is that I always got some shading/Shadows in the Glass Elements what I did not wanted... just ground..