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Richard Hebert
10-20-2008, 12:07 AM
Hi Guys,

I've got a model with a glass canopy. I'm wanting occlusion on the model but I'm getting it under the glass canopy in an area that in reality wouldn't be there. I've tried everything that I know to eliminate it in that area but what I know is extremely limited. Any thoughts on what steps I might take? Thanks to all who assist.

Richard

geothefaust
10-20-2008, 01:03 AM
What I would do, is to assign those particular polygons a different surface. Then do one of two (or both) things to reduce the size of the occlusion. First thing, copy and paste the same surface, but then go into the occlusion node and tone down the distance. This should help quite a bit.

Secondly, if this is just for a still, you could do two renders, and then comp them together to get the effect you want. I recently had to do this with something very similar. Basically just do what I was saying for the first part, but instead of rendering it out in one pass, do two (one for each part of the surface, to make it render quicker, you could even just cut out some of the geometry that wont be needed for the small area you need to capture for comping).

Anyway, I know that sounds convoluted, but it's not that bad. Personally, I'd stick with option 1 if you can.

(Long post, sorry, it's late here. :) )

Richard Hebert
10-20-2008, 01:13 AM
That's OK, it's very early here! Thanks for the rapido responso. I'll check out option 1 as this is going to be for animation. Sure nice to have you guys around.

Richard

lardbros
10-20-2008, 03:02 PM
Im sure one of the free ambient occlusion plugins respects transparency, can't remember which one, but it's probably the SGAmbOcc node, that one seems to have the best features. Although there is another one, but the name of it escapes me!

Richard Hebert
10-20-2008, 04:21 PM
Just did a little research on Photon Mapping. Are any of you guys familiar with that process and can it be applied in LightWave? That method would probably solve most ambient issues and do away with having to use occlusion nodes.

lardbros
10-20-2008, 04:30 PM
Just did a little research on Photon Mapping. Are any of you guys familiar with that process and can it be applied in LightWave? That method would probably solve most ambient issues and do away with having to use occlusion nodes.

As far as i know, it's a Vray and mental ray thing. Also is used in many other renderers. Pretty sure it's not in lightwave yet.

But i'd certainly check out those Ambient Occlusion nodes, im sure they'll do what you're after?

Here's a link to the best one:

http://www2.informatik.hu-berlin.de/~goetsch/AmbOccNode/

Richard Hebert
10-20-2008, 04:49 PM
Are you aware of any Mac compatible plugins?

lardbros
10-20-2008, 05:07 PM
Are you aware of any Mac compatible plugins?

Oh poo, guess not... i don't use a mac, so don't really know if they are or not, sorry!

Richard Hebert
10-20-2008, 05:22 PM
Just found one for the Mac. Haven't tried it yet but will let you know the results in a couple of hours. Thanks for sending me in a direction. I wasn't even aware of the various plugins available on the net. If this meets my needs I'll send them a donation for getting me through this phase of the project.

Surrealist.
10-22-2008, 02:01 AM
As far as i know, it's a Vray and mental ray thing. Also is used in many other renderers. Pretty sure it's not in lightwave yet.

But i'd certainly check out those Ambient Occlusion nodes, im sure they'll do what you're after?

Here's a link to the best one:

http://www2.informatik.hu-berlin.de/~goetsch/AmbOccNode/

I have that one. It has the option. But it did not make a difference on my test. At least the layers version. I did not try the nodes version, come to thing of it.

A solution that would also work would be to simply make the glass one sided polygons and not a solid poly object. For the cockpit that might be enough. But it just depends on what the needs are for the shot(s). I have not tried dialectic node so I don't know what that wold offer on a one sided poly group as opposed to a solid geometry.

Richard Hebert
10-22-2008, 02:27 AM
Is it something I'm doing wrong or do the Occlusion nodes (doesn't matter which one) ignore light info. whether direct or bounced. Seems like occlusion levels stay consistent regardless of light levels on the model. Like I said in earlier posts, I'm no expert on this stuff so be gentle. Thanks!

Richard

creacon
10-22-2008, 08:35 AM
The first question you need to ask is if you really need any occlusion plugin.

I know MentalRay users use this technique a lot because using final gather in MR is very slow, but it's just a crude way of faking radiosity.

I would use final gather radiosity in LW, with just a gray color in the backdrop for this kind of lighting, then just add one area light for some directional shadows. This will respect reflection, transparency, .....and it will look a lot more real.
Oh, and if you do this kind of work often, buy FPrime, it will save you tons of time.

creacon




Is it something I'm doing wrong or do the Occlusion nodes (doesn't matter which one) ignore light info. whether direct or bounced. Seems like occlusion levels stay consistent regardless of light levels on the model. Like I said in earlier posts, I'm no expert on this stuff so be gentle. Thanks!

Richard

Richard Hebert
10-22-2008, 09:24 AM
Great advice. I'll be using it on these projects. As for FPrime, well... I'll have to wait awhile before I can actually spring for it. My accountant (my wife) says funds are insufficient! OK, I actually manage the cash flow but I will be getting that plugin as soon as possible. Will cut hours down to minutes. Thanks to all of you for your insightful and cordial responses. I've visited other forums and saw the ridiculing of some beginners who really didn't have a handle on things who were just wanting to get a little knowledge. I've never witnessed that happening on this forum and attribute that to all of you. My hat comes off to all of you. :thumbsup:

Richard