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Thread: tile size bug

  1. #1

    tile size bug

    hi,

    think i found a bug - i rendered robbie the robot with different tile sizes
    his dome faceplate is a dielectric.
    i started with 128 up to 1024
    every render gave a different result to the glass dielectric
    from being clear
    to being tinted (which is what i think it was supposed to be)
    to being clear and tinted but in sections

    all with just changing the tile size.


    also, i had different render times with different tile sizes.

    also, i'm finding my cpu is not rendering at full ghz either - with the larger tiles sizes i'm not getting turbo boost mode anymore. weird.

    anyone else try rendering dielectric glass and futz with tilesizes - see if you get different results.

  2. #2
    Grumpy Faux-Waver DogBoy's Avatar
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    can you get this into a format you can submit?
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  3. #3
    www.Digitawn.co.uk rustythe1's Avatar
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    Quote Originally Posted by vonpietro View Post
    hi,

    think i found a bug - i rendered robbie the robot with different tile sizes
    his dome faceplate is a dielectric.
    i started with 128 up to 1024
    every render gave a different result to the glass dielectric
    from being clear
    to being tinted (which is what i think it was supposed to be)
    to being clear and tinted but in sections

    all with just changing the tile size.


    also, i had different render times with different tile sizes.

    also, i'm finding my cpu is not rendering at full ghz either - with the larger tiles sizes i'm not getting turbo boost mode anymore. weird.

    anyone else try rendering dielectric glass and futz with tilesizes - see if you get different results.
    regarding the tile size, that's not a bug, it will take more or less time depending on tile size, don't know where the thread is, but you have to do a little maths between the render size, tile size, and how many threads you have as tiles work with the hardware, if you don't get the correct size some of the time you can have threads running idle as they are waiting for other threads to finish and catch up before going on, (or as far as i know that's how it works, don't know the exact reason, i think it may be briefly mentioned in the docs too but not in any detail)
    Intel i7 5960X Extreme, Asus Rampage V extreme, 3x 4gb NVIDIA Geforce GTX970, 32GB DDR4 2666 corsair dominator
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  4. #4
    Electron wrangler jwiede's Avatar
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    Quote Originally Posted by rustythe1 View Post
    regarding the tile size, that's not a bug
    The differences in appearance (esp. w.r.t. coloration, and how much is colored) of the material when only tile size is adjusted definitely sounds like a BUG.
    John W.
    LW2015.3UB on MacPro(12C/24T/10.13.2),32GB RAM, NV 980ti

  5. #5
    Super Member Kryslin's Avatar
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    Re: Tile Size

    What I've found is a good starting point is to take your render size, and divide each by the tile size, and round down. Take those numbers, and multiply them. If this result is equal to or greater than the number of threads you have, you're good.

    Example:
    My render size is 800 x 600. Since a 256 x 256 tile (800 / 256 = 3, 600 / 256 = 2, 3 x 2 = 6, I have an i7 960, 8 threads) yields a result less than my total number of threads, I drop it back down to 128 x 128. This way all threads of execution are working whike rendering.

    In testing, I've noticed that either size works well, and keeps all threads saturated pretty well. Of course after the first pass, the renderer can assign multiple cores to tiles as the image nears completion.

    Note that this is what works for me; it doesn't provide for optimum rendertimes, but a more efficient CPU load. A single 1K x 1K tile will still render an 800 x 600 frame faster than any smaller tile size.
    --------
    Intel Core i7 960 @3.20 Ghz, 24 GB ram, EVGA 6GB GTX980Ti "Classified" driving 2 x HP LA2405.

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