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Iray: Render Quality Does Not Override Samples or Time

Nyghtfall3DNyghtfall3D Posts: 813
in The Commons

My latest project took Iray 4 hours 49 minutes to process 15000 Max Samples.  I've rendered it twice now, and it always stops after reaching Max Samples.

My understanding of the Progressive Rendering settings for Iray is that enabling Render Quality is supposed to override Max Samples and Time.  It doesn't.  I have Render Quality set to 10, and Rendering Converged Ratio set to 99.9%.  It never exceeded 4%.

Is this a bug, is my understsanding of the render settings wrong?

Comments

  • L'AdairL'Adair Posts: 9,479
    edited January 2016

    It's not a bug. Render Quality affects how many samples are needed to reach the Rendering Converged Ratio. Max Time is turned "off" by changing the setting to 0 (zero).

    You can go into the parameter settings and either set the upper limit higher or remove the limits altogether. Same as any parameter. Just click on the little gear icon, and then click on the Parameter Settings menu item.

    ETA (Edited to add): You can make this change in the settings without closing the "completed" render. Just click on the (incredibly small) arrow on the left side of the render window and open the Progressive Rendering section. You can change any of those settings and then the Resume button will become available. (Added for anyone who might not know this yet.)

    samples-gear-menu.jpg
    640 x 554 - 147K
    samples-parameter-settings.jpg
    720 x 826 - 208K
    Post edited by L'Adair on
  • Richard HaseltineRichard Haseltine Posts: 108,072

    Render Quality affects how much work is done at each pass, as I understand it.

  • Nyghtfall3DNyghtfall3D Posts: 813

    Thank you both.

  • L'AdairL'Adair Posts: 9,479
    Richard Haseltine said:

    Render Quality affects how much work is done at each pass, as I understand it.

    That makes sense. My observation also shows more passes, (samples,) to reach Rendering Converged Ratio. But I do tend to set the Quality higher mid-render, if I'm not happy with the results as it gets closer to the end.

  • ToborTobor Posts: 2,300
    edited January 2016

    Render Quality sets the threshold of when the Iray engine considers a pixel converged. Convergence is an estimate of when a given pixel is "done," and is derived by compariing multiple ray samples of that pixel. When the average of the results is within a threshold limit, that pixel is considered complete. 

    You typically do not need to set this value to anything but the default 1. A value of 10 will require about 10X the processing time. 

    The first question to ask is what's happening that you need to adjust the values from their defaults? It's better to tackle rendering issues by resolving the underlying problems, and not simply throwing a gaggle of ray hits in the hope Iray will rehabilitate the image. If you need to set convergence ratio to 99 and render quality to 10 in order to get a better picture, Iray is trying to tell you something is wrong.

    Post edited by Tobor on
  • L'AdairL'Adair Posts: 9,479
    Tobor said:

    Render Quality sets the threshold of when the Iray engine considers a pixel converged. Convergence is an estimate of when a given pixel is "done," and is derived by compariing multiple ray samples of that pixel. When the average of the results is within a threshold limit, that pixel is considered complete. 

    You typically do not need to set this value to anything but the default 1. A value of 10 will require about 10X the processing time. 

    The first question to ask is what's happening that you need to adjust the values from their defaults? It's better to tackle rendering issues by resolving the underlying problems, and not simply throwing a gaggle of ray hits in the hope Iray will rehabilitate the image. If you need to set convergence ratio to 99 and render quality to 10 in order to get a better picture, Iray is trying to tell you something is wrong.

    I've had many scenes that looked really good with Quality set to 1, Rendering Converged Ratio 95-100%. But I've also had scenes that looked really good at that point, look even better when I set the Quality higher. One example is this image I did for one of the contests. I wasn't happy with the amount of gloss on the man's hair, so cranked up the Quality and let it render longer. The improvement to the hair was acceptable, but the improvement to the reflections on the glasses and the champaign bottle were amazing! Now if reflections are important, I don't hesitate to up the Quality setting.
     

    Prelude to a Kiss, by L'Adair

    For a closer look at the reflections, click on the image here and go to the gallery page. The full size image is 1500px x 1200px.

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