geosphere as background

[leo_surrealismo]

hi, Can someone explain me how to setup a scene with a geosphere acting as a background and not to interfere with ilumination?
thank you!

leo

[TomG]

Why would you want to, compared to using the overrides (Direct Visibility, Reflection, Refraction etc.)?

[TomG]

(if you do have a particular reason - but it should be a good one ;) - just using a CoronaLight material with Emit Light turned off, and set the geo not to cast or receive shadows should do the trick)

[leo_surrealismo]

because I am using it on a 360 tour and I need to fake the movement within the boundaries.
I did what you told me, but it is still casting a weird shadow.

[TomG]

Best thing is to post an image showing what you mean by a weird shadow :)

[leo_surrealismo]

take a look at the images and see the weird shadow :)

[maru]

That's a known issue listed under "black highlights" here - https://support.chaos.com/hc/en-us/articles/4528311915025-Known-bugs-and-limitations


I am attaching images showing it, and a workaround.
The workaround is to split the background material into two separate Light Materials:
- material A with "emit" off
- material B with "emit" on and "occlude" off
- then plug material A into all slots of a rayswitch material
- then plug material B into "reflect override" slot of the same rayswitch material
- then apply the rayswitch material to your background object

Let me know if you need further help / explanation here.

[leo_surrealismo]

thank you! it´s working now on my scene!
have a nice day!

[leo_surrealismo]

I have noticed something,  I need this background to affect visible reflections... in this setup, I can not see how to do this.

[maru]

The material that you have plugged into "reflection override" should be affecting reflections. It doesn't seem to work like this?

[leo_surrealismo]

no, It does not.  Should I upload a scene to you?

[maru]

If you have a minimal scene, that would be great. If you prefer to send some production scene, you can PM me or upload it here: https://corona-renderer.com/upload

[leo_surrealismo]

many thanks maru.
pm sent.

[leo_surrealismo]

hi again,
could you spot what is the problem here on my setup?
I am in another project and the problem came back again. 
I have a geosphere with a rayswitch material just as corona support told me (emit off  on refract and direct override; emit On on reflect override). But when I do this, it starts reflecting my CoronaSky.  and If I unthick emit light, the reflection with glossiness of 1 are perfect, but I get black speculars.

thanks!

[PROH]

You need to put the "emit off" material into the GI slot in the Ray Switch material.

[leo_surrealismo]

yes, but look at the wrong speculars on the image.  They turn out black.

[PROH]

An empty GI slot = black light.

[leo_surrealismo]

If you see on both images, both has GI unchecked and they behave diffrently.
anyway, I tested your suggestion and still does not work.

[leo_surrealismo]

I have uploaded the scene thru dropbox, if support can look at it.

thanks.

[leo_surrealismo]

I did not manage to solve this problem.
I am in onother one and facing this problem again.
and, no, it is not because I have gi unticked.
could you guys help me out what is wrong on this setup?

[maru]

I think everything was already explained in this thread. Corona doesn't "like" fake effects such as objects not casting shadows and they can lead to shading issues. There is at least one known workaround to this, but it is not perfect. Can you show your results? Maybe then it will be possible to come up with some additional ideas.

[leo_surrealismo]

I mean, I know it is a limitation, but would it be addressed at some point?
these is the output I'm getting.... the spherical background doesn't get reflected into the kitchen backsplash.
Hopefully you could give some ideas.

[polygon3di]

In this case I use corona light with disk shape targeted instead corona sun. Try to set direction, intensity and radius, imitating the sun. The main idea that light sourse was in front of  plane with corona light material. Check that light from fake sun should be uniform. I know it`s cheating but maybe it will be acceptable for not large scene.
Here my tutor

[Tom]

Interestingly, I just discovered that I had encountered this bug in my last scene without knowing where it came from. I had thought that my backplate was the culprit but didn't have time to address the issue. So thank you @leo_surrealismo for this very informative thread.

The workaround seems effective, it's always better than fixing the bug in Photoshop :) but I see that the post dates back to 2021: so it's not planned to find a fix in a future Corona version?