Speckles with HDR lighting

[tricky]

We are running a project at the moment where the main exterior lighting is a HDR image. I have created a dome light and added the HDR, and have the subdivs set to around 32 (but I have tried 64).

No vray sun or sky.
Environment colour is black.
GI Environment (skylight) override is ticked on and set to black.
The HDR is instanced into the Reflection/Refraction environment override.

On some of my materials, I get bright speckles appearing. I have upped the samples on these materials to 32 or so, but I still get the issue. What is the best technique to get rid of these?

I am using a simple LC (1000-1500 samples) / Irmap ( typically 'high settings') setup.

The main reason we don't tend to use HDR lighting is because of these type of issues.

[jacksc02]

Have you tried clamping the image?
Sub pixel mapping on?
Are you using "use light cache for glossy rays"?

[Toko]

could you made a test with the "ray dist." parameter in your dome light?
set it to "explicit" and play with the value...

[tricky]

Have you tried clamping the image?
Sub pixel mapping on?
Are you using "use light cache for glossy rays"?

Haven't tried clamping (we are using 32 EXR files in Pshop. I will try clamping to 4 and see if that helps)
Sub pixel mapping is on.
Light cache is being used for glossy rays - pre-filter = 100, re-trace threshold = 1.0, Filter = nearest, Interp.samples = 10

[tricky]

could you made a test with the "ray dist." parameter in your dome light?
set it to "explicit" and play with the value...

I have no idea what the figure represents. The default is 100000. 100000 what? My scene is 1 unit = 1 meter.

[Toko]

if you set the ray distance parameter from "none" to "explicit" you could set the max ray distance 100cm or something else...sometimes i got speckles in my shadow pass, when i youse normal vray lights the "directional" parameter could fix these problem...and in a dome light the distance parameter could fix some speckles...
you could also try to set your dmc sampler settings as low as possible min-1 max-4 or something else

[tricky]

if you set the ray distance parameter from "none" to "explicit" you could set the max ray distance 100cm or something else...sometimes i got speckles in my shadow pass, when i youse normal vray lights the "directional" parameter could fix these problem...and in a dome light the distance parameter could fix some speckles...
you could also try to set your dmc sampler settings as low as possible min-1 max-4 or something else

Will try.

I am already using the Adaptive DMC with min=1, max = 8 and Clr thresh at 0.01.

[tricky]

if you set the ray distance parameter from "none" to "explicit" you could set the max ray distance 100cm or something else...sometimes i got speckles in my shadow pass, when i youse normal vray lights the "directional" parameter could fix these problem...and in a dome light the distance parameter could fix some speckles...
you could also try to set your dmc sampler settings as low as possible min-1 max-4 or something else

Setting to explicit 100cm makes no difference.

[kosso_olli]

I get this problem in nearly every car shot with an HDR. You can try setting the Adaptive DMC to 1 min and 10 max, uncheck use DMC sampler threshold and set the clr. tresh. to 0.003. If you have luck, the speckles dissappear.

Regards

Olvier

[Morne]

in which render element is the speckles?

if it's in the reflection, maybe its just the hdri being pixelated?

try this:

Select your light and type the following in the MaxScript listener:
$.dome_visibleOriginal=2

[tricky]

in which render element is the speckles?

if it's in the reflection, maybe its just the hdri being pixelated?

try this:

Select your light and type the following in the MaxScript listener:
$.dome_visibleOriginal=2

Will give this a try when I get a moment. For the moment (because we are in a rush) I ended up switching off 'trace reflections' in the materials that were showing the speckles. This works, but it doesn't have the subtlety of reflecting a blurry HDR.

Does *anybody* use HDRs in their rendering? They seem to give us problems like this time after time.

[rivoli]

Does *anybody* use HDRs in their rendering? They seem to give us problems like this time after time.

it can happen, depending on the scene and the dynamic range of the map. sometime there's not much left to do than clamping the output, even though it's not always necessary to go down to 1.0. often you can get away with something between 3 and 5, but it's really hdri/scene dependent. sometime turning off GI caustics helps too, but it doesn't work for all cases.

[joconnell]

Does *anybody* use HDRs in their rendering? They seem to give us problems like this time after time.

Yep - doing an entire film with vehicles almost entirely lit with hdrs. Mainly glossy reflections but at low strengths so maybe not as many things that'd cause "pings" as in your scene. Also we've a habit that if there's a sun in the shot, we paint it out in nuke first, and add in our own sunlight instead for better control over the spread of the shadows.

[tricky]

Yep - doing an entire film with vehicles almost entirely lit with hdrs. Mainly glossy reflections but at low strengths so maybe not as many things that'd cause "pings" as in your scene. Also we've a habit that if there's a sun in the shot, we paint it out in nuke first, and add in our own sunlight instead for better control over the spread of the shadows.

I might look into doing that. I thought (and assumed) that modern versions of vray would resolve these kinds of issues automatically.

Maybe if vraysun/sky system could be developed further to have clouds and treeline/building lines along the horizon, that would be a cool thing. Fat chance.

[joconnell]

I'd say that it's always going to be tough on any anti aliaser trying to smooth between such broad ranges of pixel values. If you're using any kind of blurry reflections too, all that it's doing is adding in some random variation in the direction of the reflection rays shooting from a surface so there's a good chance that a random one can hit a totally different light source from the other reflection rays. If that light source is 20 times brighter than every other one around it you'll get an imbalance in your reflection sampling and it'll translate into the final pixels. Only solution is to either clamp your render to help the sampler, turn up your light samples, or turn up the reflection samples on the material that's causing the hassle.

Do you go through a comp process at all or use the "don't affect colours" checkbox? What's the next stage for your renders after they come out of vray?