How to get 100% CPU usage instead 50% only?



is there an option to enable the full power?


(Menno Deij - van Rijswijk) #2

Probably related to hyperthreading and the program getting your core count wrong. Basically, if you have 4 cores, hyper threading will virtually double that number. But many programs that do parallel computations actually look at the number of cores and disregard hyper threading. As hyper threading is a hardware trick for creating 2 virtual processors out of 1 core, you would not gain another 50% in speed, rather only a few percent.

See comment below from @andy; this is not related to Hyperthreading.


If I remember me right I tested it for Vray some years before and the result was that HT isn’t so bad.

I see here that 75% are used after I manipulate the Neon view, than the usage is falling over the time to a very low value. Also the CPU temps are jumping and not stable high like I know it from Vray. I have no good feeling if I see this, for me it looks like the full power isn’t used.


I looked around at the web - looks like HT brings 20%…30% percent more speed. Since speed is a main property of render engines I don’t understand why not use HT. Also the speed decrease over the time looks like a bug.

(Andrew le Bihan) #5


I think I know what’s going on. We actually throttle Neon back to give Rhino more CPU cycles, but it shouldn’t be as bad as you describe. Are you using it on as very simple model? How long does each pass take?

(Andrew le Bihan) #6

And BTW - HT works quite well with Neon.


I think approx. 5 passes per second at the beginning, later more passes per second, but at very low CPU usage (10%).

(Andrew le Bihan) #8


Can you download this version of Neon and see if this works any better?

  • Andy


Hi Andy, doesn’t looks so much better.


I tested the Vray RT display mode and found that there is no full CPU usage too. Could it be that there is a general problem with the Rhino display pipeline?

(Andrew le Bihan) #11

No. I don’t think so. What processor(s) does your computer actually have?


Dual Xeon E5 2687W

(Andrew le Bihan) #13

I’ve actually been discussing this with Micha offline (because he sent me a model that is non-public). The problem is that the amount of work that Neon is doing to render the latter part of the scene is basically “not enough”…so it’s getting bogged down in house keeping tasks instead of rendering.

The solution was to increase the number of rays per pixel so that there was actually some meat to the scene using a high number of bounces in Brazil.


Interesting…is ‘rays per pixel’ controlled by any of the settings exposed in Document Properties?

(Andrew le Bihan) #15

No - it’s basically a function of how much stuff there is to render. If you have reflections, GI, transparency, lights- all of this will contribute additional ray casts per pixel.


So…but if you crank up the settings so that there’s “more for it to do” later on in the rendering, it’s not like that’s going to speed it up. It’s just the nature of this type of rendering of that kind of scene?

(Andrew le Bihan) #17