Finding cause of speckles

[tricky]

I am working on an interior scene, and I have started to notice white speckles on some of my surfaces. How do I pinpoint the cause so that I can solve the problem? In the past, this type of thing has been caused by my vraysun being visible, and setting this to off has been the solution. In this cene, my sun is turned off. I think it can also be caused by materials bouncing light around too.

What is the easiest way to sort this out? Its a real ball ache when I have 40+ materials in the scene, and 20 or 30 lights.

[Dariusz Makowski (Dadal)]

Break scene apart.

Get render passes refl/refr/ill/diff/etc etc and then once u know which channel cause issues u can start addressing them.

[tricky]

Break scene apart.

Get render passes refl/refr/ill/diff/etc etc and then once u know which channel cause issues u can start addressing them.

It seems to be on my rawref layer, so something to do with reflections. I hate this about archvis.

[joconnell]

Only thing you might be able to do is use a series of light select elements with groups of lights in each one so you can narrow down the source of the speckles to a particular light.

[Dariusz Makowski (Dadal)]

It could be caused by a texture that is pushed past 1 intensity in its settings. Have a look if any of textures is overcolor corrected or so.. Maybe bad 32bit hdr...

[glorybound]

have you done all the basic? Color Mapping, enough subdivs on the material, make sun invisible?

[Morne]

Hi Tricky

Here's my checklist for this sort of thing (not in any particular order of importance). This depends on your scene and how you decide to set things up.

* Check sun invisible
* A: VRayLightMTL, if used few options depending on how you use it. Use low multiplier not higher than 5. Tick "Compensate camera exposure" - Do not use "Direct illumination"
* B: VRayLightMTL, tick "Direct illumination" and increase Subdivs to 128 or even higher (but I recommend option A for this)
* Depending on which workflow you use, increase subdivs on your reflection shaders
* Make sure your GI settings is enough
* If you're using an HDRI for lighting, try switching it off just for troubleshooting
* Check you dont have any standard or non vray materials in the scene
* Check that bitmaps dont have a rgb ouput higher than 1

I'm sure you know the difference between speckles, noise and splotches so I wont go into that here.

In your particular case however, I would investigate reflection subdivs, light subdivs and then GI (investigate using your elements as others suggested) and I see you found something in your RAWrefl channel
Maybe worthwhile starting with an override material with a glossy reflection and see if you still get the speckles.

Could you maybe show us a crop of what the speckles look like?

[3DMK]

Try turning off all your GLASS objects & do a test render.....I often get problems like this from light rays passing through glass. If this solves the problem, just exclude the glass from the Lights.

Hope this helps

[pengo]

I'd add even through curtains sometimes so try without them too

[stevesideas]

I found a random piece of information regarding removing small spots in a render in the vray documents online. I can't for the life of me find it again but maybe Vlado or someone else can link you to it.

Edit: It might be something to do with shadow bias or cutoff possibly in the vraylight settings.

[Dariusz Makowski (Dadal)]

Did u sort it out maybe?

If its reflection maybe disable textures and see if its still there... that should narrow it down to texture issue or other mystical issue...

[tricky]

Thanks all for your detailed replies. This forum is grrrrrrr8! ;-/

I solved it, but we are running that many jobs at the mo I forgot what I did. I *think* it was something to do with a bunch of vrayies lights I had in the ceiling. I either upped the samples or reduced the shadow bias or something, and the problem seems to have gone away.

Out of interest, Shadow Bias: what the heck is it? Our vray sun always defaults to 200mm and it causes us all sorts of issues with shadows and normal maps (that is, until we reduce it). Do people just set this to zero?