Importance Sampled LIght export for Games

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Hi SideFX,

Mantra can do some good importance sampling of environment lights. Game engines cannot, thus sometimes relying on old school light domes, a la HDRShop of old. Is there a way to exploit the functions in mislighting.vfl to generate a good quality light dome? That would be handy!

Regards,
Jason
jason iversen, houdini procedural pipeline supervisor @ weta digital
also, http://www.odforce.net [www.odforce.net]
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Hi Jason,
just because i am curious…
Are light domes still being used in games?

kind regards

Olaf
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To be honest, I don't know if they're used in real games, per se, however we have a need for a high fidelity lighting environment for some non-game work being done in a game engine. I would think there games are lit more directly.
jason iversen, houdini procedural pipeline supervisor @ weta digital
also, http://www.odforce.net [www.odforce.net]
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If you bake out a HDR environment map and the game engine generates a mipmap out of it and does proper LOD'ing of the mipmaps in the engine, you should be able to get the same effect. That bright dot (>1.0) will blur out on lower mipmaps, making it more likely to get “hit” by a sample (ie, a cube texture lookup).
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Hi Mark,
twod
If you bake out a HDR environment map and the game engine generates a mipmap out of it and does proper LOD'ing of the mipmaps in the engine, you should be able to get the same effect. That bright dot (>1.0) will blur out on lower mipmaps, making it more likely to get “hit” by a sample (ie, a cube texture lookup).

The biggest issue, (I'm told) is that game engine env maps don't shadow as nicely as discrete lights. This is why we are fiddling with light domes right now.
jason iversen, houdini procedural pipeline supervisor @ weta digital
also, http://www.odforce.net [www.odforce.net]
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would lightgen help here?

http://gl.ict.usc.edu/HDRShop/lightgen/ [gl.ict.usc.edu]
Michael Goldfarb | www.odforce.net
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That's what we used to use back in the day as alluded to in the OP. I was hoping not to have to unearth hdrshop again, but I'll do it if I must.
jason iversen, houdini procedural pipeline supervisor @ weta digital
also, http://www.odforce.net [www.odforce.net]
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Hey Jason!

You're correct in saying that game engines don't use environment maps for shadowing. It's only for ambient lights (and reflections) on a dynamic context. Some engines MIGHT do shadowing on light baking but I'm not 100% if Unreal and Unity do.

For that same reason we've had to do the light dome tricks quite often even in this current generation of hardware.

We don't have any tools for this (yet) but it shouldn't be too hard to do a brute force prototype with reading in an environment map on a sphere and sampling the geo to generate lights pointing to the center.

I hope I'm understanding your question correctly

Luiz
Luiz Kruel
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Yes, you've got it. FWIW, I found an old image of HDRShop1.0.3 and the LightGen plugin and it actually worked. We got an decent increase in rendering speed over environment maps, as well as helping with shadowing. So, a win all around.
jason iversen, houdini procedural pipeline supervisor @ weta digital
also, http://www.odforce.net [www.odforce.net]
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