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Why do some Iray renders take painfully long?

DrekkanDrekkan Posts: 459
in Daz Studio Discussion
So I'll render an image of a person say a g8m character normally dressed and inside a building with a decent good amount of light so you can see him and the general area he inhabits but for some reason it will take aaaaaaages for the progress bar to begin to move upwards. One of the most common reasons an iray render might take forever is the absence of light so I have read around here but I know this certainly isn't the case with this render. What else is it commonly most likely to be?

Comments

  • alan bard newcomeralan bard newcomer Posts: 2,172

    to start what card what computer what ram etc do you have., 
    ===
    is this all scenes or one scene? 
    ---
    start with a basic ... put the character undressed on the stage and render with just the basic sky dome. note the time
    add the outfit .. repeat 
    and the building and light
    ---
    maybe repeat again with different character and diffrent outfit and different building
    does the render run only on the card or is cpu? 

     

  • alan bard newcomeralan bard newcomer Posts: 2,172

    I think when you start the render and it looks like it's just sitting that's when it's gathering maps etc and loading them... and then it starts the rendering ... so it may be something taking extra time to set up. 
    If you set the dialogue to verbose ... it will tell you what's it's doing

     

  • felisfelis Posts: 4,313

    If you look in the log Help > Troubleshooting > View Log File

    It will tell you which actions there is done with timestamps.

  • Richard HaseltineRichard Haseltine Posts: 100,804

    What sort of lights? If the figure is in a room then HDRs or Distant Lights won't do much as the walls will block them, which will not be apparent in texture Shaded Drawstyle.

  • SickleYieldSickleYield Posts: 7,634
    This can be caused by several things so I'm going to fire off the ones I check first. Iray doesn't like rendering inside a fully enclosed space. Take a wall off behind the camera if you can. The other main causes for me are layered refraction (hair with water, for example) and lots of large textures (scene contains entire arch set instead of just the part visible in the scene, and every piece of the set has 4096x textures). I especially suspect textures/geometry of the set because that long 0% phase is when it's loading textures to the graphics card. Which reminds me of another thing it does at 0% - converting any 3Delight shaders to Iray in the engine itself for use in the render. Make sure your set has Iray shaders before you hit render, too.
  • DrekkanDrekkan Posts: 459

    K sorry for not replying sooner but I'll look into this more specifically with what SickleYield stated. that's useful info. Thx everyone.

  • alan bard newcomeralan bard newcomer Posts: 2,172

    again how slow is slow? and how capable is your equipment 
    I've seen people in the forums who sometimes have to spend hours on a render and other who do them in 2 minutes. 
    If you're using a pentium on a laptop with build in 1g video card or a desktop with a couple 3080s will affect how long the render takes. 

     

  • JamesJames Posts: 1,037

    probably the render fallsback to cpu due not enough gpu vram.

    Provide us with your computer specs, especially your gpu.

  • SlimerJSpudSlimerJSpud Posts: 1,453

    Download GPU-z and start it running before you start a render. This gives you way more details about what the GPU is doing than anything built in to the OS. If the render drops to CPU because of lack of VRAM, this will be obvious. You can also find out if that happened from the Daz Studio log file. In some cases, downsizing texture files from 4K to 2K will keep this from happening with negligible loss of quality. YMMV.

    https://www.guru3d.com/files-details/gpu-z-download-techpowerup.html

    Other things I have found that slow down renders are: Curved surface light emitters. Unless you really need to see that glowing light bulb, replace it with a point light, or a spot light. For enclosed scenes, making one or two  walls disappear has been mentioned. You can also play tricks like make the ceiling 60-80% opacity to let light in.

  • nwleee_a52bfead84nwleee_a52bfead84 Posts: 108
    edited August 2022

    SlimerJSpud said:

    Download GPU-z and start it running before you start a render. This gives you way more details about what the GPU is doing than anything built in to the OS. If the render drops to CPU because of lack of VRAM, this will be obvious. You can also find out if that happened from the Daz Studio log file. In some cases, downsizing texture files from 4K to 2K will keep this from happening with negligible loss of quality. YMMV.

    Using GPU-Z what indicator should I specifically be watching.  (there is a lot of information given across 4 tabs/screens)  
    It doesn't give any information about the CPU usage, so how can I tell if the render drops to CPU?

     I was watching the "GPU Load" percentage indicator.  It never went above 95%.  
    The scene was relatively small, one unclothed Genesis 8.1 female, With (dForce) Classic Blowback Hair, 4 or 5 lights using NVIDIA Iray (MDL) renderer.

    SPECS:
    CPU: Intel i7-5820K CPU @ 3.30GHz (6 Core)
    MOTHERBOARD: ASRock X99 Extreme3, X99, 3way X-Fire & SLI, GB LAN, USB3.0
    RAM: 32 GB DDR 4 SDRAM PC4-19207
    And I just got a brand new GeForce RTX 3060 GPU (which has greatly reduced my rendering times)


    Thanks!

    Post edited by nwleee_a52bfead84 on
  • alan bard newcomeralan bard newcomer Posts: 2,172


    It doesn't give any information about the CPU usage, so how can I tell if the render drops to CPU?

     I was watching the "GPU Load" percentage indicator.  It never went above 95%.  
    The scene was relatively small, one unclothed Genesis 8.1 female, With (dForce) Classic Blowback Hair, 4 or 5 lights using NVIDIA Iray (MDL) renderer.

    SPECS:
    CPU: Intel i7-5820K CPU @ 3.30GHz (6 Core)
    MOTHERBOARD: ASRock X99 Extreme3, X99, 3way X-Fire & SLI, GB LAN, USB3.0
    RAM: 32 GB DDR 4 SDRAM PC4-19207
    And I just got a brand new GeForce RTX 3060 GPU (which has greatly reduced my rendering times)


    Thanks!

    in general if the render drops to CPU unless you  have something like battlecoder shirase limiting daz's use of the cpu 
    the first clue is your processor gets extremely noisy as it is maxed out and you can't do anything because when the daz render is using 100% of the cpu cycles.. you probably can't even use cntl alt delete to get to the task manager to stop the render...  you either wait it out ... which could be along time or do a hard stop via the start button. 
    ====
    I think there have been comments about dforce hair being a real heavy load. 

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