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Thread: GI newbie

  1. #1

    Question GI newbie

    I just purchased 9.0, having upgraded from a very old version of Lightwave. I also just downloaded the 9.2 beta and have it running. Since the old version I was using didn't do gi/radiosity I am unfamiliar with a good starting point for the gi settings.

    I have read over the docs that came with 9.0 and have looked over the examples in the 9.2 threads and obviously are missing something. All my results come out very blotchy (that is the only way I know to describe it). If I do a normal render without gi I get the results I expect and very similar to my old renders. Does my description ring a bell with anyone?

    Thanks for any advice. Feel free to point me back to the manual as I may have just missed something.

  2. #2
    Registered User ShawnStovall's Avatar
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    Increase the Rays per Evaluation, with a high enough setting you should be able to get rid of the splotches.
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  3. #3
    Respect The Architect Limbus's Avatar
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    There is also a draft of the new manual in the beta forum. Im not sure how much it says about the new GI but it cant hurt to have a look.

    Florian
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  4. #4
    Eingetragenes Mitglied Dirk's Avatar
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    I have to admit, I also think it's hard to understand GI. There are tons of options and possible methods / workflows, and render times are long, it seems to be very hard to achieve something that looks nice.

    I'd love to see a good introduction / tutorial on this subject.
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    What do I know? JBT27's Avatar
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    Quote Originally Posted by Dirk
    I have to admit, I also think it's hard to understand GI. There are tons of options and possible methods / workflows, and render times are long, it seems to be very hard to achieve something that looks nice.

    I'd love to see a good introduction / tutorial on this subject.
    A good intro video would be very handy for alot of people.

    I also agree that understanding GI and getting good results out of it is difficult - you can almost make a career just out of that, and perversely use alot of time that perhaps in many instances would be better served by a fuller understanding of more traditional cgi lighting techniques that render a great deal faster than GI.

    I like GI, and I like the potential it has for the future of cgi, but I don't think anyone should lose sight of the more conventional approaches. GI working at current speeds is still quite new, but in many instances still way too slow for alot of projects.

    Julian.

  6. #6
    Thanks for the info. I am trying to improve my render with the Rays per Evaluation value, but are not having much luck yet. I am at 800 on RPE and the results still look about the same (a bit better, but not much). Perhaps I should describe my scene.

    I have an enclosed room with a few objects scattered about. I have three objects with luminosity set to 500% and ambient set to 25%. I thought I could light the scene without any true lights being defined. Am I wrong in this?

    I will keep trying, never fear. Regardless, 9.2 looks very exciting and I can't wait to try more of the features 9.x gives me over what I was using.

    Thanks again all.

  7. #7
    Respect The Architect Limbus's Avatar
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    Quote Originally Posted by dragon57
    Thanks for the info. I am trying to improve my render with the Rays per Evaluation value, but are not having much luck yet. I am at 800 on RPE and the results still look about the same (a bit better, but not much). Perhaps I should describe my scene.
    Can you post all your settings and maybe th results you have so far?

    I have an enclosed room with a few objects scattered about. I have three objects with luminosity set to 500% and ambient set to 25%. I thought I could light the scene without any true lights being defined. Am I wrong in this?
    If your scene is still too blotchi with 800 RPE I would try the following (assuming that you use interpolated GI):

    - lower your RPE to somewhere around 256, you can alwayways increase it later
    - Set Tolerance to something between 0.5 and 0.2
    - increase the MES

    - Use more than 1 AA pass and/or multiple photoreal MB passes. This will help to clean up the blotches

    Download the manual for 9.2 Openbeta 14. There are some parts about the new GI in there.

    Florian
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  8. #8
    Limbus, thanks for the recommendations. I will try them after the current render finishes. Where can I download the manual for the beta? I have searched around but haven't found the link yet.

    Thanks again.

  9. #9
    Respect The Architect Limbus's Avatar
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    Quote Originally Posted by dragon57
    Where can I download the manual for the beta? I have searched around but haven't found the link yet.
    There is a link in the LW v9.2 Documentation Forum in the Beta Forum. The thread is called LightWave v9.2 Documentation

    Florian
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  10. #10
    post scene or at least screen grab and tell us your object scale (is it built in proper-natural scale).
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  11. #11
    I have changed my approach and am getting good results although I still don't know where I was going wrong. I am now using three area lights and the results are good and the blotches are totally gone. The gi settings are the same as before except I reduced the power of the luminous surfaces since I added lights to the scene.

    Increasing the MES in my original scene did help, but eliminated some shadows and the result still wasn't as good as it should have been. I knew gi was hard to get a handle on, but sheesh .

    As to the scale question, my objects are scaled to real life dimensions. The room is 10m long, 4m deep and 3m high.

    I also can't find the beta doc. I don't see a 9.2 documentation forum when I login to the forums. I have emailed Newtek support to see if my account has all the appropriate permissions.

    Thanks for all the help people, it is appreciated.

  12. #12
    Respect The Architect Limbus's Avatar
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    Quote Originally Posted by dragon57
    I
    I also can't find the beta doc. I don't see a 9.2 documentation forum when I login to the forums. I have emailed Newtek support to see if my account has all the appropriate permissions.
    I guess then you dont have permissions for the beta board yet. It should apear at the very bottom of the forum page.

    Florian
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  13. #13
    Quote Originally Posted by Limbus
    I guess then you dont have permissions for the beta board yet. It should apear at the very bottom of the forum page.

    Florian
    Yes! The Newtek elves must have been busy last night. Today I can see all the forums and are downloading the 9.2 docs now. Thanks again.

  14. #14
    Professional amateur Amurrell's Avatar
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    Been messin' around with GI and found that increasing MES and RPE work good for smoothing things out, however when animating I get a strobing effect. I know this is in part due to the random nature of the evaluation placment in radiosity calculations (the evaluation points aren't in the same places in each frame), but is there a way to minimize the effect? More bounces? Would post a clip but, not sure if the server will allow 4 megs of a cheap, slapshod animation. Oh I guess it will...or not. Get an error while trying to upload, but if anyone knows what I'm talking about I think it would be helpful to others on this thread.
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  15. #15
    Dreamer Ztreem's Avatar
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    They only flicker if and object move or a light move, because it's affecting the scene and has to be recalculated, but if nothing moves it's should not flicker. High MES values makes the flicker more visible so on way to make it go away is to lower the MES. There's also a second way and it's to set AA to 1 and set MB passes to 10 or something and get rid of the splotches that way. Lowering the MES and using the MB passes works quite good. The interpolated radiosity is very good now compared to what it used to be in regards of flickering.

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