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Mental Ray Distributed Rendering Issues
show user profile  gimpgutter
Hey all! I haven't been here for years, but thought it would be a good resource for information on Mental Ray and Max. Although I worked for an MEP engineering firm, we've recently decided to produce some architectural visualization using Revit and Max 2012. Luckily for me, we have a few spare Revit machines to use for distributed rendering. However, I'm having an issue with utilizing more than 3 machines.

I have modified the distributed rendering settings in Mental Ray to utilize 4 additional machines on top of my own machine. I then did a series of tests measuring the rendering time for one frame, varying the number of machines each time.

Each machine is fitted with a Core I7 (quad core w/ HT), 12 gigs of ram, and a copy of Max. They are all connected by a gigabit LAN. The scene is an exterior view of a multi-story building at 1080p resolution and uses Final Gather for a daylight system. Because of NDA, I cannot post any more information on the scene contents.

Here are the results:
- 1 machine (No dist. rend.) = 4 m 2s
- 2 machines = 2m 15s
- 3 machines = 1m 41s
- 4 machines = 1m 30s
- 5 machines = 2m 15s

As you can see, the 5th machine offers no advantage in rendering time. I did another test at 720p and the times increased for both the 4th and 5th added machines.

Can anyone tell me what's going on here? Would it be more advantageous to use Backburner?
read 1066 times
9/28/2011 10:47:38 PM (last edit: 9/28/2011 10:47:38 PM)
show user profile  Nik Clark
I've posted almost exactly the same here several times.

The benefits of Distributed rendering lessen after adding the third box. I think it's not the most efficient process, and this shows up the limitations of it's distributed nature.

Also, never use one machine that's slower than the rest. It will always hold the rest up.

For stills, use two or three boxes. For animation, use backburner as normal. This is what I've found to be the fastest.

read 1065 times
9/28/2011 10:53:04 PM (last edit: 9/28/2011 10:53:04 PM)
show user profile  gimpgutter
Good advice. I just did another test and got an unusual result.

I reran the 1080p test with 5 machines, now the render time is 1:22. At least it's now quicker than 4 machines, albeit minimally.
read 1060 times
9/28/2011 10:55:51 PM (last edit: 9/28/2011 10:55:51 PM)
show user profile  Nik Clark
It's disappointing that the performance doesn't scale up as you'd hope. I have five dual quad exon boxes at work, and using three is faster than using five with mental ray DBR nearly every time. I haven't worked out if there's anything specific that causes it. I don't think it's network limitations.

BTW, good to see you back here, Nick.

read 1057 times
9/28/2011 10:58:46 PM (last edit: 9/28/2011 10:58:46 PM)
show user profile  gimpgutter
I'll tell ya, it's almost surreal. I used Max throughout high school and learned a great deal on my own and from this forum. However, I decided I should use my brain and become a mechanical engineer, so I pretty much abandoned all creative 3D.

I've been working for an MEP firm for four years now, with the last 6 months focusing heavily on a transition into Revit from AutoCAD. As part of this, we've decided to begin a small marketing and visualization department, which I'm lucky enough to spearhead. I've got two other guys with Max and Revit experience under me.

So now, I get to combine my engineering knowledge with my love for 3D visualization to create industry leading engineering visualization (and boss some people around). I wish I had the opportunity to show off my work and talk about my experiences, but its all very proprietary and secretive.

That said, I'd like to increase my involvement with Maxforums and hopefully offer up some advice on relating engineering to visualization.
read 1052 times
9/28/2011 11:06:54 PM (last edit: 9/28/2011 11:06:54 PM)
show user profile  Nik Clark
Glad to hear things have worked out well for you!

Nobody ever leaves Maxforums. They just wander off for a while.

read 1042 times
9/28/2011 11:35:25 PM (last edit: 9/28/2011 11:35:25 PM)
show user profile  Mr_Stabby
its to do with sync time vs work time, ideally if the machines were doing work all the time instead of waiting on each other you'd see improvement but that is hard to achieve sometimes. You can try adjusting bucket size i guess but really its just MR's half arsed implementation thats to blame for this.

read 1039 times
9/28/2011 11:40:37 PM (last edit: 9/28/2011 11:40:37 PM)
show user profile  khamski
Hmm.. Isn't there any answer from MR team?

read 1026 times
9/29/2011 1:02:57 PM (last edit: 9/29/2011 1:02:57 PM)
show user profile  Andypandy7
"Nobody ever leaves Maxforums. They just wander off for a while. "

This is true, still visiting since 2000-ish

Nice to see you gimp!


read 1014 times
9/29/2011 6:58:54 PM (last edit: 9/29/2011 6:58:54 PM)
show user profile  gimpgutter
Holy shite, I've been here over 10 years....
read 1002 times
9/29/2011 9:38:58 PM (last edit: 9/29/2011 9:38:58 PM)
show user profile  c0
Please ignore my post if not considered constructive...just trying to help....

Do all machines have 100% exact same hardware / software configuration? Was Windows installed manually each time, or were the machines 'imaged' from a single installation source? You have used 3 machines giving you the fastest render speeds. Have you also tried shuffling machines and check whether using 3 different machines give you equally fast results? Have you confirmed all machines are equal before upscaling. I would also download a big file over the network on each computer and make sure transfer speeds are similar all across the board. ...I must confess it sounds like it simply does not upscale better than 3 to 4 nodes by your experiments though....
read 992 times
9/30/2011 1:26:45 AM (last edit: 9/30/2011 1:31:58 AM)
show user profile  gimpgutter
c0: You're asking excellent questions.

Here are my answers:
- All machines are 100% identical
- All machines are using an imaged version of Windows 7
- I have shuffled the machines around and got similar results
- The transfer speeds appeared fine, but I didn't do an in-depth check of all machines
read 976 times
9/30/2011 2:34:01 PM (last edit: 9/30/2011 2:34:01 PM)
show user profile  khamski
Ok here what i got after a lil bit of googlin'.
You need to use both methods simultaneously.

lol they call it "teams".
So you can create DBR teams in BB rendering.

== Backburner and DBR ==
Backburner works with Distributed Bucket Rendering (DBR), also known as Satellite Rendering, having the advantage that you can have multiple machines on your render farm rendering on the same frame AND still have your workstation free for work AND use Backburner as a queue.

To get this working, you need to edit the max.rayhosts file in the mentalray subdirectory on one machine A in the farm to which you will be
submitting the backburner job. To this file, you add the names/IP addresses of other machines B, C, D... that should serve as satellite
nodes, in total up to 8 CPUs.

You then activate the 'Distributed Render' option in your scene (the list of nodes does not matter) and submit your render job using the 'Net
Render' option. You then assign only machine A to the job, which will then trigger machines B, C, D... for satellite rendering. Of course, you
need to save the rendered image, as the result will not be displayed on an Virtual Frame Buffer.


Hope it helps.

p.s. Also i read that people have the same problem as yours so it's a known MR "feature".

read 971 times
9/30/2011 3:12:42 PM (last edit: 9/30/2011 3:31:31 PM)
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