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Radiance
09-12-2005, 07:11 AM
Hello all,

I'm rather new to LW8.3 (i'm from the ancient LW 5.6 era), and I'm exploring HDRI lighting. It all works quite nicely, but I'm having a problem with it:

I can't get hypervoxels to cast any shadows in a purely-HDRI lighted scene.
I've tried Image World and Textured Environment (Backdrop panel), and Radiosity is set to Backdrop only.
Is this normal?

I've switched on every imaginable shadow option, even though some make absolutely no sense (but hey, who knows, right?). And the manual just doesn't cover HDRI shadows - unbelievable that even with over a 1000 pages, LW still has so many uncovered features/tricks/shortcuts and what not.

However, I have noticed, that using Monte Carlo radiosity does produce shadows. But since Backdrop only renders so much faster, I would still like to know if I've missed something.

Can anyone shed some "light" on this, please?

Cheers,
William

erikals
10-04-2005, 07:51 PM
Interesting queation, you got it to work.
I've read some posts earlier about HV and shadow issues, so it might be that HDRI doesnt work with HV.

If interested I can do a simple test, but not now. Need sleep. :sleeping:

ACLOBO
10-05-2005, 02:57 AM
If I am understanding what you are saying and you are using backdrop only for your radiosity, then that is probably the problem. Backdrop only does render faster, but it is less accurate and only takes your Backdrop image into comsideration for lighting your poly scenes. Hypervoxels are a different story as they are not make of polygons, but are volumetric and procedurally generated (that is why you can get close to then and new details show up). Monte Carlo must be the only mode that can handle taking those voxels into account since they are not simple geometry.

My suggestion is if you have Fprime, test your voxel setting in VIPER and then render your voxel scene with Fprime as it will render the voxels and its Monte Carlo setting is very fast compared to Lightwave's.

-Adrian

walfridson
10-05-2005, 03:08 AM
try lightgen for hdrishop. you get bunch of lights based on the hdri. works well for sas anyway

erikals
10-05-2005, 05:41 AM
Yupp, the Backdrop only mode doesn't work I'm afraid..

Also make sure the HDRI light has high contrast. (this didn't seem to be a problem in your case though :))

operation
10-05-2005, 04:02 PM
Background and Montecarlo are different method. You can't get the same result.. but long to explain.

to make it very very simple (don't blame me please ! ): backround radiosity is a bit like a Skylight or an occlusion shader.
Montecarlo is much accurate solution, calculating truely boucing and overcasting light.

It's a basic explaination again ! search on the net if you are are looking for me precise explaination. but keep that it mind, that will help you.

Yes, you can you use Lightgen to convert an HDRI map to a group of lights with color and intensity from the HDRI map.

If you are looking only for shadow , I will do it this way:
Use Luxigon ( a domelight and select only hypervoxel to cast shadows) and exclude all other objects.

you will get a light from your backfround radiosity and shadows from an hidden lightdome.

an other solution:
http://www.kolumbus.fi/erkki.halkka/plugpak/
Overcaster plugin.

Unless a correct password is given, the PlugPak scripts will run in "Unregistered" mode, which is fully functional and free, but has some annoying popups and a random 1-30 second delay.

it may help you ( AMBIMAGE and SHADOW plugin could helpyou)...

keep us informed :thumbsup: :D

Radiance
10-06-2005, 07:55 AM
Thanks for the explanation, guys.
Yeah, the "domed lighting" to generate soft shadows and simulate radiosity is much used by me, hehe.
I will look into Lightgen, it sounds quite interesting. And I reckon it will produce better results than a standard luxigon.

Cheers!