Wrong render settings? (Black glass reflections)

[tomasbird]

Hi everyone,
I'm returning to Blender after many years and I started toying with Yafaray this time. So far so good, but I've always had problems with certain staff about proper render settings and lighting. Right now I am experiencing these weird black parts in my testing render for glass Susan, see pic below.


Is this the expected result? What can I do to fix that? I have and HDRI map set for the scene, there are two light sources (planes with Mesh Light).

Render settings looks like this:


The glass material is simple preset:


Thank you guys for any tips

[Samo]

Increase ray depth anytime you find black areas on glass

PD: if the black areas don't go away it is because the glass is reflecting a black area, maybe a black background?

[tomasbird]

Increase ray depth anytime you find black areas on glass

PD: if the black areas don't go away it is because the glass is reflecting a black area, maybe a black background?

Ray depth it was. Thanks a ton man!

[tomasbird]

Now if I could bother you with one more issues, which are these weird black dots on the final render result? I've read it's because of HDRI maps, I tried with and without, changing from spherical to angular, but no matter what I do there are these black dots:

[Samo]

It is probably a bug. Can you upload the scene please. You can tools to upload attachments below the message's body when you post a message.

[tomasbird]

It is probably a bug. Can you upload the scene please. You can tools to upload attachments below the message's body when you post a message.

I changed a lot of settings tried different setups and eventually the black dots went away - so I don't have the scene setup where the dots were happening, sorry

[tomasbird]

However right now I run into problem of the white dots/noise in my renders. I need to do an outdoors scene - animation to be precise, couple cars passing each other, nothing too complicated and I need to make it look somewhat decent. I was reading up on lighting for exteriors and I figured that Path Tracing with IBL lighting only should be enough to get a decent results, if I am mistaken please correct me here .
As you can see on pictures below, there is a lot of noise/white dots.
16 samples ibl/path, Path Tracing, cm: photons


64 samples ibl/path, Path Tracing, cm: none


I though to get rid of them increasing the samples (both IBL and Path) is gonna do the trick, but there is not much difference. Even with 512 samples there is lot of noise/white dots, and the render times goes up dramatically. How do I further reduce the noise and make the result as clear as possible? Is that all done in the AA/Noise control tab?

[David Bluecame]

Hello,

Thank you for your feedback. If possible we would need scenes showing the problems (with the textures used in them) so I can try to replicate the problem and (hopefully) fix it.

Best regards!

[tomasbird]

Hello,

Thank you for your feedback. If possible we would need scenes showing the problems (with the textures used in them) so I can try to replicate the problem and (hopefully) fix it.

Best regards!

Hi David,
alright, here is the scene, sorry for the size (130mb) and shitty hosting. The HDRI map I'm using is quite huge, hence the size
http://www.megafileupload.com/rkt0/scene.rar

[David Bluecame]

Hello,

Thank you for the scene. This issue is related to this:
http://yafaray.org/node/727

The problem is caused by the very high intensity of the sun in the HDR image. When the HDR is sampled to illuminate the scene, when the samples are coming from the sun, it causes very brigtht spots in the materials.

This is something I have to solve somehow. In the mean time there is a trick you can try: please try "clamp samples = 1.5" for example. This limits the intensity of each sample in the materials. Strictly speaking the illumination would not be "physically correct" when using clamping, but it can reduce noise and "fireflies". Please let me know if this helps for now.

About the black dots, I'm very interested on see why they happened. It would be very useful if you can replicate the problem and send me a scene causing the black dots.

What operating system are you using? 32 or 64bit?

Thanks and best regards. David.

[tomasbird]

The problem is caused by the very high intensity of the sun in the HDR image. When the HDR is sampled to illuminate the scene, when the samples are coming from the sun, it causes very brigtht spots in the materials.

This is something I have to solve somehow. In the mean time there is a trick you can try: please try "clamp samples = 1.5" for example. This limits the intensity of each sample in the materials. Strictly speaking the illumination would not be "physically correct" when using clamping, but it can reduce noise and "fireflies". Please let me know if this helps for now.

It seems that setting clamp samples to 1.5 solved the issue - I think I should have set it a tad bit higher to get completely rid of the white noise. Thank you very much. I will stick to this workaround or use a different HDR image - can you tell by eye which one is gonna cause problems and which one won't?

Before:
(Blender 2.77 with YafaRay v2.1.1.2016)


After:
(Blender 2.77 with YafaRay v2.1.1.2016)


--------------------------

I also tried to render the same scene with previous version of Yafa, just to see if that could be the issue. It was not, but the car pain material does look better in that one
(Blender 2.73 with YafaRay v0.1.5 - unofficial build 2015-03-29-beta2)

About the black dots, I'm very interested on see why they happened. It would be very useful if you can replicate the problem and send me a scene causing the black dots.

I'm really sorry, I only have the scene where it does not happen anymore. I tried to reproduce it right now, but without success. If I ever run into it again, I'll make sure to send it to you.

What operating system are you using? 32 or 64bit?

64bit

[David Bluecame]

Interesting what you said about the difference in the material respect to the old version. I will take a look at that, why that difference.

I'm glad this helped you. Best regards!