Why is Team Render slower than Single Render?

[KAB]

Hello

I am a bit disappointed, I have connected a second iMac (4 cores) called "B" to my standard render iMac (10 cores) with Thunderbolt to render an image sequence.

The strange thing is that if I render with iMac "A" alone, the rendering process is faster than with team render.

Can someone please explain to me what I am doing wrong?

Many thanks, Best,
Katharina

[TomG]

Probably the size of the data transfer chunks is set too low, which means more time is lost sending data back and forth than is gained in rendering. Under Render Settings, Corona, Team Render, check if Automatic is set (the default). Try changing it to Arbitrated (experimental). If that alone doesn't improve things, lower the client update interval (send data back and forth less often) maybe try something like 20 or 30 seconds rather than 5, and raise the Max size of packet, try something like 128 or 256.

This can be resolution dependent, so the higher the resolution, the longer the interval and the larger the Max size of packet you want to try (basically if you see very tiny thin strips being rendered by TR, time to make these adjustments). Let us know which of the above helps!

PS - also you can render through TR Server which does not have this problem.

[KAB]

Hi TomG

Thanks for your fast response. I will  try the settings you said and also will try the "Team Render Server". With the "Team Render Server I had the Problem with the login of the Webinterface: I should enter "admin" as username, but what should be my password? The one for my Corona license is not working, also not the one for my iMac-User-Login. How di I figure out that password?

[KAB]

Hi TomG

I have now tested the first variant of yours.Once with Arbitrated (experimental) and the values 20 / 128 and another time with 30 / 256.

Unfortunately, both speech times are completely identical to the original attempt with the standard team render setting on "Automatic".

Therefore, unfortunately, no improvement.

[TomG]

Curious that it made no difference at all. Any difference in the amount of RAM on both machines? (Could be the second machine is running out). Also, what are the render times, in case the slower machine just doesn't have time to contribute anything before the render completes.

For the password, it's something set within and controlled by TR Server. The default set by the TR Server if you don't change it is admin and admin, for user name and password.

[BigAl3D]

I would add that we don't know the size of the frames and how long the animation is? If it's a short animation and uses very large textures, then you're better off with a single machine since all the time to transfer all the assets to the second machine will eat up any speed gains. How fast if your network? The other thing I've found, and this isn't a Corona only thing, is if the scene is difficult to render and your second machine is much slower, then at some point the fast machine will finish and will sit idle until the slow machine finishes that final frame.

If you have any items that could benefit from baked cache files, that could also speed things up so the slow machine doesn't have to calculate, just load the cache files that the fast machine created.

[KAB]

Hi

Thanks for your advice. I send attached 2 screenshots of my iMacs.

The render time per frame is 4:45 min. each. , regardless if I use a Thunderbolt to connect the Macs together and do team renders or just render with the 10-core-iMac alone.

The 4-core iMac is actually an older device.

I want to render a movie with a tracking shot where the camera is pointed head-on at a building facade and moves along it. The scene has surface spread clones, lots of materials, and a complex model. In total, the image sequence would be 500 frames long.

I have attached one frame as a png for you. Can you take this opportunity to explain why the metal (circled in orange) makes such funny spots here? If I render only one image alone / no animation, I don't have this problem.

@BigAI3D how do I make such a "baked cache file" and how do I make that specifically available for the render client as well?

Best, Katharina

[jojorender]

Hi KAB,
How do you get to the 4:45min per frame? Did you set a pass, time or noise limit?
When you say “team render slower than single render” this is regarding a single frame test render and not the entire animation, correct?
When you render a single frame your 2 Macs render the single frame together. Due to overhead, etc. this could take longer than single machine render…
For animations, your 500 frames will get split in half. Frames 0-249 gets rendered by your 10 core machine, 250-500 by your 4 core Mac.
Setting a time limit p. frame for an animation with 2 very different CPU’s would be “dangerous”
since your 4-core Mac would need more than double the time to reach the same image quality as your 10 core Mac.
In your case, probably best to figure out the amount of passes needed for the desired image quality. In any case, the 4-core Mac will be a lot slower to reach these # of passes, but once the 10 core finishes the 250 frames, it will half the remaining frames from the 4 core and start rendering those. You will definitely save some time “team-rendering” the animation.
 
Also, not sure if you tried to setup “load UHD from file” (maybe not since you have an outdoor scene), but if so, most likely only your fast Mac can find that file and the slower Mac needs to calculate the UHD from scratch (for every frame) making matters worse. You can confirm if the UHD file gets loaded in the TR console.   

@Corona team:
Any news if we will get “relative path support” for the UHD cache?

[BigAl3D]

@jojorender

I think he means if he renders the image locally with his 10-core Mac, it's faster than using Team Render with both machines. I have had this issue too, but changing the packet sizes fixed that for the most part. I will say that sometimes, it just better to only use the fastest machines.

[mmarcotic]

@Jojo render,
I should have a testing build this week that has the fix for relative paths in Team Rendering, so fingers crossed.