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Thread: Fast Stencil Light Volumes for Deferred Shading

  1. #11
    Senior Member OpenGL Guru Dark Photon's Avatar
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    Oct 2004
    Quote Originally Posted by kRogue View Post
    It is sort-of-ish like it, but not quite the same.
    Pretty slick! Thanks for sharing.

  2. #12
    Member Regular Contributor
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    Jan 2005
    Quote Originally Posted by Dark Photon View Post
    Sure doesn't sound like it.
    Thanks. I understood what deferred shading/lighting means but I was not sure how narrow the distinction is. I think if a technique doesn't have the same drawbacks as these two maybe it doesn't make sense to apply the terminology. But the same idea of filling a full screen buffer of sorts for later sampling applies. So I wasn't sure.

    What this does sound like is what I've seen called "Deferred Shadows", "Shadow Collector", or "Screen-space Shadow Mask".
    Good good, I was fishing for some jargon terms for which to search with

    I remember searching around for antialiasing techniques for ages until I found the right name for what I wanted (I think it's called morphological??) but unfortunately I could not find any public code (for preprocessing purposes) and the one or two papers was really terse so it would have been a major project to roll from scratch. I'd hoped GIMP would have a filter but it's AA was just a mindless kernel. My goal actually there is to generate perfect alpha test contours which I am pretty sure is possible but I've never seen it in a new game (the grass billboards and such are always bumpy up close)

    Point is knowing the right code words goes a long way.

    I'm guessing by this you don't mean behind the shadows, but behind the nearest opaque fragment, which is where the occlusion field (shadows) is sampled. (?)
    Right. Except I said shadows because the Z buffer is already initialized wherever a shadow exists going into the second phase. And if a pixel is already in front of (or on) the shadow then the test is moot but would probably have to be done anyway.

    Quote Originally Posted by kRogue View Post
    the standard lighting shader, then loops over the lights in the range [lightBegin, lightEnd), the light is considered active if the lightbitmask locigcal-anded with light bitfield buffer matches with the lightbitmask. The use I have for this was having a light go through a portal. The face of the portal was always planar so the light volume it case was always ok to just do flipping. You can see the demos of this pet project at: ... sighs it has been a long time since I have had the time to do that project
    Out of curiosity. Is the portal here like a magic portal? Or is it like how light enters a room through a doorway even though the source is around the corner?
    Last edited by michagl; 09-17-2012 at 08:01 PM. Reason: kRogue quote
    God have mercy on the soul that wanted hard decimal points and pure ctor conversion in GLSL.

  3. #13
    Advanced Member Frequent Contributor
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    Apr 2009
    Out of curiosity. Is the portal here like a magic portal? Or is it like how light enters a room through a doorway even though the source is around the corner?
    Just look at the videos.. but in a nutshell, a portal is a connection between two places, ala the game Portal. The thing I made had the light travel through the portals casting light volumes to get lighting correct...

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