Glass rendering with transparency-which lighting?

[Kris_LW]

Hello,

I have issues with a glass rendering with transparency.
I need it later with transparency/ alpha for photoshop, preferably with shadow and reflection.
The following problems:
- If I set all lights with transmission 0, I get a bad result. I despair at the light source, does anyone have ideas?
- I have set the plane for shadow and reflection to zero in the camera, otherwise I will lose transparency again. But I can't get the shadow and reflection that way.

It's probably quite simple, but I'm going round in circles...

This is how the lighting appears:

But the colours should look like this:

I hope someone can help me.

Greetings,

Kris

[lee_griggs]

Are you using standard_surface.transmit_aovs?

[Kris_LW]

Hi Lee, thank you for your reply. Transmit AOV in the materials ist enabled and the Arnold Skydome and Arnold Sky ist set to 0 in Transmission. I´m slowly getting there with changing the material settings. The big question is now, can I get a shadow out of a plane with shadow_matte and without losing all my light (which happened already when I tried...)?

[lee_griggs]

The shadow_mate isn't giving you a shadow? Is transmission_weight for the glass at 1?

Can you upload the scene?

[Kris_LW]

Hi Lee, the shadow matte is giving me no shadow and is also deleting my transparency in the alpha. 
I must be missing something. Here is a test file. I converted it to 3ds (I didn´t know that I can´t upload c4d files), I hope it works. 
Thank you and greetings, Kris

[lee_griggs]

You can Zip the C4D file and upload it here.

[Kris_LW]

Ah! Here it is 🙂

[Kris_LW]

Hi Lee, do you have an idea for my problem?
Many greetings, Kris

@lee_griggs 

[Kris_LW]

I´m sorry for the duplicate, I´ll continue here.
I couldn´t find it anymore, I´m new to the forum.

Here I send u a file where you can see my problem. I also put a cube in to compare. 

[lee_griggs · Accepted solution]

I see a shadow when I add an HDR map to the skydome_light.color. This is with a new shadow_matte shader assigned to the plane.

[lee_griggs · Accepted solution]

Thin_walled was enabled. It should only be enabled for single-sided geometry without any thickness. Also, your IOR was 0. It should be 1.5 for glass. These might be what is causing you issues.

Here is the scene. You will need to replace the HDR map with one of your own.

[Kris_LW]

Thank you Lee! I took your file  and put in my own HDR texture.
I have a shadow but my glasses are not transparent/translucent:

Do you also have a solution to render the shadow on an extra layer with multi-pass?

Thank you for you effort!

[lee_griggs · Accepted solution]

You can't see an alpha for the cubes because the plane is in the way. If I move the plane to one side you can see the glass alpha. 

Also, the skydome light is visible in the transmission of the cube. If you reduce it to zero you can see the alpha for the cubes.

[Kris_LW]

Oookaaayyy, got it 🤣
My mistake was that I thought the shadow_matte makes the plane completely invisible!

I learned:
To solve my problem I must do one rendering only with the glasses and alpha and another rendering with the shadow from shadow_matte and put them together in Photoshop.

One last quastion on this:
If I don´t have a transparent object and want to render it on alpha with the shadow_matte, how can I get a file with multiple layers and an extra shadow layer? As it is possible with the standard c4d renderer.
I don´t knwo how to do it with c4dtoa. I hope you know what I mean.

Thank you so much! 

[Kris_LW]

@lee_griggs 

This is what I was searching for:

I guess it´s not possible with c4dtoa, I have to use another program.

[lee_griggs]

You can use Takes to setup different variations of the scene (one with the Plane enabled and one with disabled, etc), and render each take to its output file. If you just want the shadow as a separate layer for comp, then you can add the shadow_matte and shadow_mask AOVs.

https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_core_ac_shadow_matte_html

[lee_griggs]

You might find these tutorials useful:

https://www.youtube.com/watch?v=-lEdyBUuWP8

https://www.youtube.com/watch?v=350LeWYinW4

https://www.youtube.com/watch?v=Q7DlalC5bjw