Background plate causing glitch with Advanced options in the Environment, Background & Atmosphere render setup panel ?

[dave]

Setting up a scene in 3ds Max 2018 (.4 update) and using MAXtoA 2.1.945, I use the Advanced options in the Environment, Background & Atmosphere render setup panel.

I have an HDRI (.hdr) as the scene Environment Map in the Environment and Effects, Common Parameters panel.

I have a backplate (.tif) image and use it in the Background (Backplate) panel in the Environment, Background & Atmosphere panel - using Custom map.

There seems to be a problem with how the backplate is being processed when seen through a transparent object, in my case glass windows. I have attached and image that shows what I have found.

With no glass the interior of my car renders as I expect. Seats, dash etc all render correctly. Shown in image labelled 1.

But, when I add glass using my own shader (but also tested with the glass shader in the Arnold examples pack downloaded from your website) I get a strange pass through of the backplate showing in my objects behind the glass. You can see this in the image labelled 2. The backplate that is shown in the objects is also reflected on the bonnet (hood) of the car.

Switching off Internal Reflections in the Specular setup of the material helps slightly, see image labelled 3. But the dash is still showing this backplate pass through glitch.

Finally I changed the backplate to Environment and all objects and reflections through the glass are as expected.

From this I can only assume that the Custom Map backplate is causing these transparency glitches.

I see on your web pages (https://support.solidangle.com/pages/viewpage.action?pageId=40665249) that you state : "Background is considered deprecated and will be removed in a future release.".

Is there any work around to this glitch, or anything planned to replace the backplate functionality ?

Any help greatly appreciated,

Dave

[michiel.van.gasse]

Can you upload a simple scene that repreduces the problem?

[dave]

Yup, here is the link to download a cutdown of that scene.

I rescaled the background HDRI, and removed most of the geometry.

If you hit render it will render the view you see in 2. in the image above.

Change the glass texture to disable internal reflections and you will get 3. - better, but still showing glitch in dashboard.

Go to render setup and change from custom map background to environment to show things as in 4 (lower res hdri though).

Dave

Download file 64 MB :

Scene

[dave]

Wrong link above - this is correct :

Scene file : 65 MB

[michiel.van.gasse]

arnold-glitch-cutdown-merge.zip

It rendered idd with the glitch, it could be the blur plugin, some setting or somthing buggy.

I've just merged the objects into a new scene and added the maps + settings again and it renders fine now.

Here is also the working file.

[dave]

Thanks for taking the time to look at the problem, and confirming what I experience, Michiel.

I, too, have completely merged my scene once before into a fresh file and this glitch has re-occured.

There must be some setting which is causing this glitch. Seems odd, as it occurs with only a few objects, all using arnold shaders.

No idea what the blur plugin is about?

I'll try and hunt it down.

Dave

[dave]

Thanks Michiel for taking the time to look at that.

But, I have found the bug.

I had adjusted the Ray Depth for specular above 1. Which is absolutely necessary, and explained in the documentation, to get correct reflections inside my headlamps (through glass, then bouncing about the reflectors).

So, this is a confirmed BUG :

If you adjust the Specular Ray Depth above 1 in the Render Setup : Arnold panel you get this transparent effect bug to objects behind glass/transparent objects.

Any Arnold representatives reading ?

Dave

[ashley.handscomb.retallack]

It seems to be a bug related to the [deprecated] Max_Sky background shader when you make it visible to spec reflection

So setting the background image so it's not visible to specular rays should prevent the issue from appearing, I've attached a simplifed repo here

repro.zip

[dave]

Thanks for looking into this Ashley. I looked at your file. To get it to work I had to link in also the "shadow" and "specular transmission" with the glass material to get it working correctly. Attached image shows what I had to do.

This gave the results I expected.

If the background shader is deprecated (as I did mention in my original post) what is the correct method to use backplates in Arnold ?

Dave