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CPU Vs Card Vs both??

AlfawulfAlfawulf Posts: 174
in New Users

When rendering in Iray, what's the bonuses of CPU Vs card??

Is both working together recomended??

Comments

  • brimstoneomegabrimstoneomega Posts: 343

    Iray is an nVidia software, and thus will only work with an nVidia GPU, with the higher the memory and cuda cores the better. Higher memory will alow you to use more characters, prop, ext. because the engine off loads the geometry and textures to your GPU, and thus if you have a huge scene it can eat up that memory and then the card won't be able to handle it. Cuda cors are the processing unit in an nVidia card, and thus the more you have the fast the card. Think of Cuda cores as CPU core in this regard. CPU renders will take much much longer then GPU renders, but won't suffer the issue of running out of memory that a card may encounter.

    I tend to leave my CPU out of renders, because it makes my AIO freak out and run like a fighter jet with it's afterburners running, and also my PC turns as sluggish as, well, a slug. 

    That said, both working together will make the render go faster, but when I did do renders with both, in the log files I would see that my CPU did about one iterations to like 50 of the GPU so I felt it wasn't worth it myself.

  • KitsumoKitsumo Posts: 1,216

    If you want to be totally sure, try it both ways. You can use the Iray Benchmark Scene to test your results each time. Using your CPU may or may not speed things up, depending on your hardware. In some cases, using the CPU can slow things down, because obviously the GPU can't do anything until the CPU gives it instructions. So, if you had your CPU working on rendering, it may not be able to send instructions to the GPU fast enough, especially if you have a fast GPU. It would be like having a restaurant manager mopping floors and trying to manage all the employees at the same time.

     
  • AJ2112AJ2112 Posts: 1,416

    From my experience, I really didn't notice much difference in render speeds, with various cards, but did notice a difference in cpu.  HIgh quality video cards, has better faster performance in preview window, example 670 to 1080, both cards rendered at about the same speed even with cpu but 1080 card performance in preview window was amazingly faster. 

  • IllidanstormIllidanstorm Posts: 655
    I have a 1080ti and 1080 ryzen and noticed that when I leave cpu off it renders faster than with the cpu. Also I'm able to do other things like posing the next scene and browsing with only gpu rendering.
  • glaseyeglaseye Posts: 1,312
    edited June 2018

    You can always try a test-scene rendered with CPU only, GPU only and both, and comapre the time....

    SickleYield made a testscene for this that might be useful:

    https://www.daz3d.com/forums/discussion/53771/iray-starter-scene-post-your-benchmarks/p1

    edit -oops- link was already posted 2 posts up....

    Post edited by glaseye on
  • AlfawulfAlfawulf Posts: 174

    Thanx for all the input guys!!

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