Light samples multiplier significant for certain corona-shaders?

[3dboomerang]

Hi,

I was getting some "splots" on cars I was creating for the library, so I added more light samples, in the multiplier. To my surprise, the higher I went, not only did the splots go away, the carpaint itself became brighter.

This to the degree that it stabilizes somewhat around "50" !!! - Not much added value after this.

But 50 is insainly high for a value which's default is 2, so I'm pretty sure I'm doing something wrong.

Check renders attached, darkest one has the default of 2, then 25 samples, and 50 samples. 75 and 100 samples give nearly the same results as 50 samples.

The carpaint is made up from a Blend-shader which contains 2 corona-MTL's.
Lighting is HDRI + Corona Sun, nothing fancy.

Any idea's?

[Nejc Kilar]

This looks super weird. I'd too like to hear what is up here :)

[maru]

This definitely, absolutely should not be happening. Can you please provide more details? Which version of Corona and host software is this? (Max/C4D/other)
Are you 100% sure that you changed Light Samples Multiplier, and not some other parameter, like Max Sample Intensity or Max Ray Depth?
Could you provide a simple reproduction scene (e.g. a teapot with this material) and send it using the uploader: https://corona-renderer.com/upload

Thanks in advance!

[3dboomerang]

Hey, thanks for looking into it.

Maru, I sent you the scene, collected.

This is what I'm thinking atm:
Is it possible I'm getting "better" reflections with increased lighting samples from the HDRI, making it brighter? The default 2, in conjunction with THIS hdri might be the problem? This particular HDRI needed more? Bad HDRI?

The renders indicate it's the blend-shader materials (carrim and carpaint are both blend-shaders, with two standard Corona MTL's in each) that are creating different results with the HDRI getting more light-samples.

Which version of Corona and host software is this? (Max/C4D/other)
3D Studio Max 2020 + Corona 5

Are you 100% sure that you changed Light Samples Multiplier, and not some other parameter, like Max Sample Intensity or Max Ray Depth?
Yes

Could you provide a simple reproduction scene (e.g. a teapot with this material) and send it using the uploader: https://corona-renderer.com/upload
I sent the scene with an HDRI giving the same problems. All the HDRI's of this source are giving the same problem.

When I plug in a different manufacturer like from Peter Guthrie, the problems seem to be gone.

Grts

[maru]

Thanks for the scene and the message. I will look into this as soon as possible.

[maru]

Reproduced, logged.
(Internal ID=492438579)

Note: this happens only when the reflections override is enabled in Render Setup > Scene. It seems to be yet another issue related to the enviro overrides.

[3dboomerang]

ok, ty

[rowmanns]

Hi,

The original issue of "spots" when using environment overrides was fixed in the latest v8 daily build: https://forum.corona-renderer.com/index.php?topic=33839.msg190180#msg190180

Also the material no longer changes colour when increasing the LSM, however you shouldn't need to do this now :)

Cheers,

Rowan