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    Shadow algorithm

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    sebh

    Posts : 1
    Join date : 2009-02-05

    Shadow algorithm

    Post by sebh on Thu Feb 05, 2009 2:43 pm

    Hi!

    Congrats for your engine.

    I just want to know which algorithm do you used for your shadow. It seems that it's shadow mapping but do you use some kind of PCF, variance or exponential shadow mapping?

    Keep up the good work! Smile


    PS: I have written an potal based engine few years ago but it was with shadow volume... Screenshot and source code on my website Wink

    orenk2k
    Admin

    Posts : 11
    Join date : 2009-02-01
    Location : Isreal

    Re: Shadow algorithm

    Post by orenk2k on Thu Feb 05, 2009 3:07 pm

    hi
    i used to do shadows using shadow volume tech, but they are not supporting none opaque surfaces (such as fences, trees etc) and not to mention translucent materials, they have lots of drawbacks (still, they could be enabled via cvar, and works with shadow mapping as well) so i'm using variance shadow mapping as they are more forgiving than regular shadow mapping.
    thanks and bye

    mikfig

    Posts : 4
    Join date : 2009-03-05

    Light bleeding

    Post by mikfig on Thu Mar 05, 2009 2:59 am

    I looked at the slides for variance shadow mapping, and I was wondering if you were experiencing any problems with light bleeding. If so, how did you go about fixing them?

    Thanks,
    Mikfig

    orenk2k
    Admin

    Posts : 11
    Join date : 2009-02-01
    Location : Isreal

    Re: Shadow algorithm

    Post by orenk2k on Thu Mar 05, 2009 11:01 am

    hi
    i had at first, but now i don't, if you search the bleeding i think you will find but it is not very clear where they are any more.
    you can't fix it (unless you do more samples and you end up doing some brute force pcf), but you can reduce it by darkening the penumbra regions.
    this could be done by modifying the 'result' (which you compute right now as the shadow occlusion value) so that any values below some threshold will be mapped to 0 and the rest will be mapped to 1, so basically you clamp the result into [0..1] range when the result is less than your threshold.
    for more info you can read "gpu gems 3 - summed area variance shadow maps - 8.4.3", thanks to nvidia it is now public Smile

    mikfig

    Posts : 4
    Join date : 2009-03-05

    Re: Shadow algorithm

    Post by mikfig on Fri Mar 06, 2009 2:37 am

    Ok thanks. Very Happy

    Mikfig

    baocai

    Posts : 1
    Join date : 2011-04-26

    Re: Shadow algorithm

    Post by baocai on Tue Apr 26, 2011 5:27 am

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