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Thread: Vray - Progressive Path Tracing

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    Veteran Member Tim Nelson's Avatar
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    Default Vray - Progressive Path Tracing

    There hasn't been much discusssion here about this new method in Vray (PPT for short) It seems very much like the results typical to Maxwell, render times included. Here is a quick excerpt from the Vray help file describing it:

    "Typically, computing the image goes through several separate tasks - for example, caustics calculations, light cache computation, irradiance cache computation, and final image sampling. While the user receives visual feedback through some of these stages, the final image is completed only at the end of the last stage - the intermediate results cannot be used.

    Progressive path tracing, on the other hand, is a method for incremental computation of the whole image at once. The user can stop the calculation at any time and use the intermediate results, if they are good enough. In addition, with path tracing, the user has only a few controls to worry about and it is very easy for set up."


    I haven't had a chance to use PPT much until this project, but so far I am really happy with how it works.

    Here is one PPT rendered after about 4.5 hours originally at 1600 pixels wide. The quality of the lighting is outstanding, but of course there is still some heavy grain.



    But the great thing is you can save the PPT calculation (another form of light cache) and re-use it as your secondary bounce combined with irradience map for the first bounce. This completely eliminates the grain that was in the PPT only rendering. And it rendered in about 10 minutes at the same resolution. Unfortunately the lighting solution isn't as nice - this is especially apparent at the shelves in the back.



    The nice thing though, is that you can then take both of these and blend them in Photoshop until you have something that looks nice. I'm don't normally put noise in my renderings, so I may or may not use this method for my final renderings. But I wonder how it would look if I let it render for 8 hours? Probably much less grain. Here is my final image of the 2 blended together, plus some adjustment to levels & a little glow.



    Anyways, just thought some of you would be interested, plus I couldn't sleep. It seems Vray is giving Maxwell a dose of their own medicine.
    Tim Nelson
    timnelson3d.com

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    Veteran Member Chad Warner's Avatar
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    Default Re: Vray - Progressive Path Tracing

    I'm glad you couldn't sleep! I had read about the PPT method, but I had only seen grainy images created with it....this helps. I would prefer a less grainy image with lower light quality than the other way around, and if using the ppt file and re-use it, then this is a great solution.

    Do you have any idea how this method works with animation?

    -Chad

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    Veteran Member Tim Nelson's Avatar
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    Default Re: Vray - Progressive Path Tracing

    I don't think this was meant to be used in animation. For that, I think you would use the standard light cache in animation mode. But this is the beginning for PPT so it will probably get better in future releases.
    Tim Nelson
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    Default Re: Vray - Progressive Path Tracing

    what version of vray supports PPT - were using 1.46.10 but i think that version 1.5 has just been released. Am i correct and has the PPT just come in on the 1.5 release?

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    Veteran Member Tim Nelson's Avatar
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    Default Re: Vray - Progressive Path Tracing

    They haven't released the offical 1.5 yet, but they are currently at 1.46.15. which has the PPT feature. Most of the bugs seem like they have been fixed, so its got to be getting really close.
    Tim Nelson
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    Veteran Member jucaro's Avatar
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    Default Re: Vray - Progressive Path Tracing

    Tim, How about PPT an interior scene lit by daylight and no artificial lighting.

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    Veteran Member Tim Nelson's Avatar
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    Default Re: Vray - Progressive Path Tracing

    No sun either & just environment light? I'll see what I can do.
    Tim Nelson
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    Veteran Member jucaro's Avatar
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    Default Re: Vray - Progressive Path Tracing

    I mean 1 directional light as the sun and nothing more, since VRay has no sun yet, as compared to maxwell. (hmnn.. VRaySun hehehe)

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    Veteran Member Ernest Burden's Avatar
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    Default Re: Vray - Progressive Path Tracing

    Quote Originally Posted by Tim Nelson
    But I wonder how it would look if I let it render for 8 hours?
    Anyways, just thought some of you would be interested, plus I couldn't sleep.
    Well, Tim. How about you get an actual night's sleep and find out? We'll all be happier in the morning.
    Ernest Burden III
    AcmeDigital
    architectural rendering.

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    Senior Member pixelperfectg's Avatar
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    Default Re: Vray - Progressive Path Tracing

    One neat trick (provided you have Dreamscape), is that PPT will pick up the sky colors from Dreamscape.

    Here's a quick PPT test with no VRay lights...just the one Dreamscape Sun and VRay GI enabled (PPT of course). The GI color is coming directly from the DS atmosphere.

    http://www.jeffpatton.net/cg-post/VRay-ppt-DS.avi

    Note: The flickering is coming from a "bug" in Dreamscape. I forgot to reset max before rendering the animation. It seems that if you adjust the cloud settings, you must restart max before rendering a sequence....else it produces this flickering.

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