Unwanted halo in ground reflections

[wddr]

Here are a couple of images from a project I'm working on at the moment. The first is a screenshot, not exactly right yet, but the shadows and reflections are how I want them.

The second is the same image after rendering, you can see there's a kind of halo all around the ground reflections. I get this whether I create a normal render or a real-time render. The ground is a flat plane with a metallic paint applied. Any suggestions for fixing it? Detailed shadows, detailed indirect illumination and ground direct illumination are all turned on, and I've tried increasing the ray bounces and global illumination quality. What I really don't understand is why I see the same effect in the real-time render, I thought this was meant to be the same as just letting the image sit?

Thanks in advance...
Matt

[guest84672]

Make sure to check "detailed indirect illumination" in the realtime tab.

[wddr]

Hi Thomas,

Detailed Indirect Illumination is turned on.

Here's another image from a different angle. At the bottom left is a bright reflection, but you can still see the halo, around the cable in particular.

Thanks,
Matt

[guest84672]

Hmm - this is strange. Can you share the bip file?

[wddr]

Yes, I can share. File size is about 21.5Mb. Where should I send/upload?

Thanks for your help,
Matt

[guest84672]

Send to support@luxion.com. Use one of the free services like sendthisfile or yousendit.

Thanks!

[wddr]

Just sent the file...

[JeffM]

After looking at the file, I find the problem is due to the material having the roughness and metal roughness very close in value.

The roughness is the roughness of the clearcoat on the metallic paint, and the metal roughness controls the spread of the metal "layer" in the paint. Typically you want a low, usually 0, roughness and a higher metal roughness to get the shiny paint effect.

Try lowering the roughness to 0 or increase the metal roughness a bit to around .1.

If you like the roughness setting exactly where they are, then lowering the glossy samples setting to around 8 or so will help get rid of the halo in this case.

I'll see if we can address issue further in the program as well.

[wddr]

Hi Jeff,

I've been experimenting with some of your suggestions, here's what I've found:

First I tried lowering the material's metal samples, to 16 and then to 8, but I couldn't really see much difference, the halo was definitely still there.

Then I tried increasing the metal roughness value. Increasing it to 0.1 helped, but I needed to take it up to 0.4 for the halo to disappear. But this also had the effect of making the material seem a bit dull, it had lost its sparkle.

Next I decreased the roughness value right down to zero, but again I couldn't really see that this affected anything, the halo was still visible.

Since the metal roughness value had been the one that had changed things, the next thing I tried was to set this value at 0.25, and the metal samples to 16. And this is what really changed things, the halo almost totally disappeared. The colour was a bit grey, so I changed the Base values to bring it back again. The result is in the image below, but in case anyone else has similar issues, here's the settings:

Material Parameters

Material Type		Metallic Paint
Base (RGB)		24,0,24
Metal (RGB)		235,78,167
Roughness		0.010
Metal Roughness		0.250
Metal Coverage		0.320
IOR		1.450
Glossy		Yes
Metal Samples		16

Render Quality

Samples		16
Ray Bounces		8
Anti Aliasing		2
Shadow Quality		2.000
Global Illumination Quality		4.000
Pixel Filter Size		1.5
DOF Quality		3.000
Sharp Shadows		Yes
Sharper Texture Filtering		No

One thing I really wanted to say as well was thanks for your help, I'd been expecting a reply in maybe a week or so, but to get advice that actually helped after a couple of hours is fantastic! Thanks again,
Matt

[Speedster]

That's one of the things we can count on from the KS team- they "really are there for us"!  Nice model, and I'm glad the halo issue was resolved, and thanks for sharing the solutions with us.  Nice model, also!  What did you model it in?  One comment, though- perhaps the plug tip would look better gold plated?
Bill G

[wddr]

Hi Bill,

Yes, you're right about the plug, I'd used an anodized finish in the images, changing it to gold looks a lot better. The model is from a project I worked on looking at ways of personalising data storage, I'm just creating some renderings so I can put it on my website. The models are fairly simple, all done in Solidworks.

Matt