3D Max not utilizing CPU

[Anonymous]

I have 3D Studio Max 9 x64 and when I try rendering a scene I open my Task Manager to see my CPU usage and I notice Max only uses 23%-38% and just moves within those precentage.

I have a quad core PC, and while Max renders all the CPU's are working but not at a 100%? When using Mental Ray rendering all the CPU shoots upto 100%, but using default scanline doesnt utilize them all.

I previously had a 2.4ghz pc, was hoping a quad core would drastically cut my render time. Does anyone know why this is? Is there a way I can get Max to use all 4 cpu's at 100% during rendering?

I am running on Windows Vista Ultimate x64 and running 3D Max 9 x64
-Quad Core 2.4
-3GB Ram
-ATI Radeon 2900 Pro

I attached a screenshot of my Task Manager while Max was rendering.

[Anonymous]

Hi mess_37,

I use only Mental Ray but Scanline for Hair and Fur pass to composite later.

[Anonymous]

Does this happen through the entire render or just in the beginning?
It could be that part of global illumination can only be computed using one core (like renderman in maya for example).
This definitely seems unusual. Try testing this with another renderer (download a demo).

It will make it much easier to trace the problem then

[Anonymous]

yes it happens during the entire render, the cpu usage fluctuates but never goes above ~45%.

Where can I download another renderer?

I know Mental Ray uses 100% CPU usage, its only when I use default scanline all the CPU's arent utilized.

[Anonymous · Accepted solution]

This is normal,
Not all of the algorithms are multithreaded so they can only use one cpu at the time.
Things like particles, hair/fur passes, scene translation/cleanups and so on can only use one cpu so during the different phases of a render it is normal to have only one cpu working.

think of it this way, if you are painting in some painting program it would be silly to have 4cpu's trying to calculate what you are doing, the processes would overwrite eachother and result in loads of reduntant work and ultimately less performance.

cheers

[Anonymous]

Have you confirmed that Max is set to Multithreaded in Preferences? As mentioned, what you're actually rendering has an impact on CPU usage, but honestly, a lot of the render components are multithreaded, so perhaps it's specific to the scene. Have you tried other tests to see if Scanline does use all cores?

[Anonymous]

Yes, I made sure multi-threading is set "On" in the preferences menu, I think Kurt is right about the scene not requring multiple CPU's to render.
I tried rendering another max file I downloaded, and I noticed all 4 CPU's are going at about ~90-100% using Scanline.

I assumed that a lot of components in Max are capable of rendering using multiple CPU's (as mentioned by Maneswar). My scene is failry simple, object, materials/meshes and lighting.

[Anonymous]

You want max to use all your cpu power ?.... you answered it yourself.....use mental ray. Like almost every other GI renderer for Max... like brazil, finalrender and vray , mental ray uses buckets (core threads) for rendering. If you use the scanline renderer be aware, that the scanliner only can use 1 thread for rendering finally which means if you have a dual core 50% and if you have a quad core 25% of cpu capacity.

The scanliner can use more threads for preparing lights, calculating displacement, shadows, motion blur and more in seperate threads...
so in preparing the render more cpu power is used but in rendering it is only on thread... so even most times the scanliner is faster than mental ray, with a quad core .. ore even a double quad core mental can be much much more faster.

[Anonymous]

That has not been my experience. Scanline is multithreaded and will use all CPU's as soon as it can. Create a test scene that'll take a few seconds to render, say 1000 teapots, add a light, then hit render on Scanline. Both CPU's will be used.

[Anonymous]

hmmm, on my scene I did have lighting, but scanline still doesnt use all 4 cpu's. Also scanline was rendering 1~2 second faster (per frame) then mental ray, even though mental ray used all 4 cpu's.

[Anonymous]

Ok then, i'l give you one that will make your head burn.
Using the exact same scene, with v-ray renderer. Rendering it at 1600X1200 uses all 4 cpu's at 100% and when rendering at 5400 X 3600, it drops to 50%.
I thought it was due to the fact that i was using Backburner, with a lot of proxies (makes large files to transfer through the network), but it does the exact same when rendering locally.
Plus I don't have anything very special in the scene: No fur, no smoke, no dof, no lens effects, no blur, no caustics, simple hdri...

I'm currently using 60% of the RAM and there is no activity on the hdd during rendering.

Anybody got a clue?


Intel Core2 Quad Q9400@2.66 ghz, 8GB Corsair XMS DDr2, Vista X64, Max2009 Design X64, V-Ray 1.5 X64... want more?

[Anonymous]

Got the same exact problem in Maya 2010 using MR. Simple scenes that pin all 8 cores in a Render View preview use only 23-30% in a batch render. Not only that, but, the same scene rendering on dual core machines only uses 50% of available CPU cores. Usually 1 core maxed out while the other sits there looking stupid.

I've seen the reported a number of times over the years but in the end never seems to get answered by MR/MI, Adesk or anyone else.. Btm Line,, if all cores max out in a render-view preview only to see 25% useage in batch-render, then thats a issue with batch-render not the scene. I suspect a thread or memory issue with the "auto" options in Batch-Render option box..