How to get an infinite floor and a sportlight that is also reflecting in the floor with C4D+redshift?

[shine-negative]

![Hi,
Sounds easy when you read the thread-title.
For my animation work, I use infinite floors. That way, I am not limited in camera movements.
My environment contains a floor (disc) and a Dome light.
In the Dome light I set a HDR as texture and enable the back-plate. With the back-plate image, I define the background color.
I add an RS Object tag to the floor and enable the matte shadow ("receive shadows from matte" enabled).
And I enable the general Matte in the same tag and set the reflection scale to 1."
The floor itself is in fact invisible. But with the tag, I get shadows.
I then create floor material and replace the "RS Standard"node with a matte shadow caster and enabled "Background is environment. I did this in order to get reflections too.
Works perfect.
But now I would like to highlight the object with a spot light. I add a spotlight above the object. The object gets highlighted, but I don't see the light spot on the floor. In fact, that makes sense because the floor itself is not visible. That is why I need to work with tags and shadow casters to get shadows and reflections on an infinite environment. My question is, how do I get the spot on the floor?
The picture shows the object, floating above the floor. Everything is fine except that I don't see any Spot. Can someone help me with this?

[Dr. Sassi]

Hi shine-negative,

Use a second pass with the RS Objet Tag not set to Matte. Compose the shot in "post". AFAIK, anything else will not work, as you have set conflicting targets; the Floor is seen or set to Background; you can't have it both ways while having a perfect result. There might be some tricks somewhere; I haven't seen it with Redshift so far in a convincing way.

Perhaps use the Overwrite Material option and an AOV light pass. I would try to set a reflection AOV pass with the Light pass. In that way, you have all data to compose it. Since I have no idea about your scene, this will work or not.

As a side note: At the moment you have reflections enabled in the RS Object, the effect will be already compromised, more or less. I would try to set a reflection AOV pass with the Light pass. In that way, you have all data to compose it. Since I have no idea about your scene, this will work or not. The Diffuse Scale is the way to receive this, but at the same time, it compromises the result, from my point of view. Full Reflection can't have full Diffuse at the same time, again, one or the other, or both half the way. Not idea. Multi-pass (AOV) will allows for a nice balance.

For future questions, please attach an example c4d file. Thank you.

All the best

[shine-negative]

Hi Dr. Sassi, I was in fact trying to add an example file but could not find a way to do that. Where is the button to add attachments?

[Dr. Sassi]

Hi shine-negative,

You need to go to the three dots, choose edit, and then there is a row of icons, a picture icon, and an empty "page" icon; that's the one.

Files in ".c4d" format are accepted, and those must be small: Example files.

Enjoy your weekend

[shine-negative]

Thank you Dr. Sassi. find attached a sample scene. [Sample_Environment.zip](Invalid file type. Allowed types are: .png, .jpg, .bmp, .txt, .c4d, .jpeg)

[shine-negative]

zip does not work. Second try. Material (png) won't upload. Please us this link.

[Dr. Sassi]

Thanks for the Dropbox Link, shin-negative.

As mentioned, sometimes information is conflicting. We use AOVs with Takes and Multipass-Compositing to get all that anyway.
Multipass compositing is the favorable way anyway, as many "post" adjustments can be made without re-rendering.

You can set up the scene as you need it in one Take.
In the next Take, you must produce and Puzzle Matte to separate the scene; in your example, the Floor forms the object (Platonic).
Besides that, an AOV for the Light that is in question is needed; with the Puzzle Matte taking the object out, you can then Compositing the Light into the image (Add).

This leaves the question, is the Spot-light, the Dome-, and the Area-light driving GI for the Light that the Floor would bounce off to the Platonic?
If so, the Floor need to have the HDRI used in the Dome Light projected onto the Floor to give a proper setup. In the scene, the Floor is blue, so the bounce of any light could be based on that blue, simplifying the setup.

https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20230319_CV4_2023_drs_23_RSbg_21.zip

In your file was only one image file. So the attached result is missing the ".hdr" file.

As a side note, for example, radiance AKA'.hdr" is fine, but in any production, I would avoid those. They have no color management, and one never knows what color spaced they originally were based on; they are only 8bit/channel, multiplied by a fourth to get the higher values (RGBE). Nothing that should be used if the quality is critical.

My best wishes for your project.