Help setting up Distributed Rendering - Dark bands and incorrect colour in DR

[ikercito]

Hi all,

I recently aquired a new machine to act as a render node to my main workstation. I've been since trying to get Distributed rendering to work, but something is not working.

My main computer has my whole 3D work drive networked, with all the files required available to my node. Node has DrServer and Backburner Server launched. Workstation has either DrServer, Backburner Server and Manager launched (i've tried different combinations everytime).

Before launching render I open Asset Tracking and either Resolve Paths to UNC location (which points the files to Z:\\workstation\...) or Retarget Common Root (to \\workstation\...) I've tried both, then I enable Distributed Render in Corona, Search LAN, and it correctly find the node (if DrServer is launched on workstation it finds it too, but i guess it is useless isn't it?). I launch the render....

It starts in both computers (can't really see whats on the node since it's minimized, but looks fine). In 60 seconds node syncs with workstation and this is what i get.... A black bar along the image everytime I do it.

Can anyone help me out please?

[lucamatto]

Hi, I have the same problem with some files...with others the image rendered with distribuited render  is more clear then the image rendered with only one PC (no matter wich PC is used).

[Lucutus]

On the first look i would guess your two machines have different gamma settings.

check input an output gmma settings on both machines.

greetz

Lucutus

[ikercito]

Thanks Lucutus for your tip, it looks like a very probable cause... But unfortunately gamma is set the same in both computers.

I've been trying a few things and still can't get it to work. I've made sure the paths are correct and reachable for both computers. Even checked DEBUG mode and looked at the temporary EXRs the node sends. They look very coarse and dark, is this supposed to be a normal thing?

What I've noticed is that the render starts fine on the workstation and once the node syncs, the black band kicks in, alternatively... first sync on the lower side of the image, second sync on top and so on... The original image progressively gets darker. That's why I'm guessing it is in fact a gamma issue, but as i said, gamma is set the same on both computers.

Could anyone give me a hint on what's happening?

[Lucutus]

have you tried to render the same image on every single machine seperatly and compared the result?

greetz

Lucutus

[ikercito]

I trying right that now Lucutus.

Launched the DR from workstation, stopped it, and now i'm rendering the scene locally on workstation, and the "received_scene.max" from DrServer/DrData on the node.

For now they look identical... we'll see after an hour. Will report back with the comparison results

[maru]

What 3ds max versions are you using (on both master and slaves)? Did you check gamma in 3ds max settings, in save image window, and in Corona settings?

[ikercito]

Hi guys,

This is the comparison from both renders. It's still quite raw and rough, didn't take time to set the lighting properly. I've checked with the eyedropper in different areas and both images are equal. Might be just a little difference of +/-1 every now and then, probably due to different noise patterns. But I think this leaves the "gamma drama" out of the question...

Now I'm completely lost on what the problem could be...

Maru: I'm using Max 2013 64-bit on both computers, both saved as EXR with gamma 1.0 and then converted to 16 bit in Photoshop. It's just the same if I save as jpeg with gamma 2,2. Can't find any gamma settings inside Corona though... (so I probably never touched them)

I'm currently rendering a Distributed render to compare with the previous separate renders. Starts to look much darker since the first couple of syncs.... :(

[lucamatto]

Hi, I'm using 3ds max 2014. The gamma settings are the same on both machines, if I render separatly on each computer the image is identical...but if I use distribuite rendering the image is incorrect...

Thank you.

[ikercito]

Hi Lucamatto, that's exactly what I'm trying to figure out.

This is a comparison of the Distributed Render against both the Workstation and Node renders separately.

Image from the DR is quite darker that the others, although doesn't seem to be a 1,0 to 2,2 gamma mismatch. Which leaves me quite stunned. I don't quite understand what's going on...

Notice the red arrow, it's showing one of the black bands that appear during the sync. Not very noticeable this time, but definitely totally incompatible with a production render...!

[Lucutus]

@ikercito

Have you tried a scene without textures? Just to sort out the the texture import as origin of the error.

greetz Lucutus

[ikercito]

Hi guys,

Just like Lucutus said, I've tried a scene without textures in Distributed Render, and it came out OK!

Then... it should be something related to textures. But what? I tested a scene individually on both computers and they both matched. But if I launch it straight from DR the above thing happens. Is this some kind of bug?

I have no idea what's going on...

[Lucutus]

in this case i guess it could be some issue relating the gamma input value for the textures.

Greetz Lucutus

[ikercito]

Hi, I guess you could be right. But, the input gamma should already be embedded on the file i'm sending to the node,... right? I mean... It works fine rendering on the node by itself. Or maybe you refer to the input of the file incoming from the node?

I've seen a few other posts about this same problem on the forum, but i think only one was resolved, and it didn't work for me. So it's not an isolated problem I guess.

Gosh... i suppose the developers are pretty busy preparing the launch of 1.0, but I'd be very grateful if they could shed some light in this :(

[borisquezadaa]

Is it a possibility that the architecture of both workstation+render are different?. Meaning different processors (amd intel).
Cause there is some calculation involved  that adress specific instructions in CPU's that (Shooting in the dark here) maybe delivers sligthly different results between CPU architectures?.
I know for fact that irradiance for animation in vray MUST be calculed in one single pc cause of this issue. Maybe the hd/uhd cache is calculated in each pc just instead in one and are sligthly different.
For DR Corona calculates hd cache in each render node and then merges the results?... or just one pc calculates and then is distributed to render nodes?.
One way to discard this would be maybe using PT/PT?..

Other wild idea is that sometimes IES files doesnt appear on assets tracking. That could be a problem.