I'm not an expert on negative light but I recall Bruce had it. Anyway, it removes illumination rather than adds it. Birn showed an example of using it to fake a shadow (so as to speed render time). Say you had a ball. You could light it from the front with a normal light. You could then setup an anti-light that doesn't cast shadows (so it shines through the ball) and also have the anti-light not illimunate (or in this case darken) the ball (apparently some apps allow that?). When I saw it added to Bryce 4 or 5, I didn't really know what to use it for. Birn has a few examples but it still doesn't seem absolutely necessary. Marc (Digital Lighting & Rendering by Jeremy Birn, George Maestri (Editor) )

I've never saw much need for negative light until reading Birn's book. There are some tricks where it looks of use (and a gel or cookie won't do the same thing). Not really a big deal, just curious. Thanks for the info on the light brightness. It is one of those things I'd've have (hopefully) uncovered on my own but with the slow GI render speeds, it might have taken a few days. Definitely worth experimenting, too, of course. Marc

Thanks, guys. Useful stuff. Hey, sfdex, I noticed your spot light was very bright. I take it you really need to crank it up for a good bounced light? My plan was to have two bulb light sources but since they are also illuminating the scene, I can't crank them up. Looks like I need separate lighting on the reflected surfaces. Or was the light really 200% (I didn't know it could go to 2000% but never tried...)? While I'm on the topic, is it possible to do negative light in CS2? Thanks, Marc

And a very effective scene it is! Very nice! I have a similar concept in mind although in my case, I was considering interior lights (essentially a pair of candles both off scene). Just wanted to make sure I was on the right track before venturing down the path. GI renders are slooow. Thanks! Marc

Marc

Tnanks, Mik. Good suggestions.

I may have to do a post-render blur on the bottle shadow if it is a problem in the final scene. On the glass color, the scene will be a fantasy scene with some faeries and a rustic appearence so hopefully an off color in the glass won't look odd. I'm still experimenting with a subtle glass irregularity in the bump channel (there is a ripple there now but it is probably too faint at the moment.) Thanks! Marc

I'm not satisfied with the shaders yet but my thought was to broaden the highlight. I still wanted the small bright highlight to indicate glass but I was looking for some broader color to help show the shape of the glass.

So I used Mark D's iridesence shader to create a highlight that has a small white spot where the two lights create white spots and then a broad, dim color region. Not really satisfied with the result yet but I think the technique is promising.

Things I'd still like to fix (and would love suggestions on): The caustics for the glass base are too bright. In my actual scene, the arrangement will be such that this is probably not an issue. But any ideas on adjusting this?

The bottle shadow's internal detail is too crisp. Is there a way to blur this (without CS3-beta ;-)? I'm using GL with indirect light and caustics.

Marc

Thank you! I've had to change my scene concept. I was going to have a thief holding this chalice with a ghost materializing behind her but after experimenting I can't get the ghost effect I was looking for. I think I could use DCG's Fake Frensel but it would take a ton of work to remove the unwanted (interior) edges. What I'd really want is something to extract the surface polygons of a multi-layer model (like a poser figure with clothing on) but I'm not sure how to do such a thing. Another option is to separately render the ghost as a solid object that composite it in with transparency but I don't think I could get that to look very good. So, the scene will instead have demon materializing (I think it will be beter this way). While figuring out how to rework the scene, though, I decided to do another, shorter project. I'll probably post a WIP on that later tonight if my GI render doesn't take too long ;-) Marc

Hi, Eric, Thanks for the detailed comments. I learned a few things about how Carrara works in the process. These WIP posts really are useful. Marc

In the final scene, I may play around with a scratch and dent effect on the gold but I'm not sure it will be too noticable (the chalice will be small in the scene) so I may not bother.

Off to the next stage of the project. This time around, my intent is to put together drafts of the two characters pretty quickly, put in a placeholders for most of the walls and objects and getting the lighting right before proceeding. After the lighting is close, I'll go back to the characters and other props. Part of the reason for this is I'm really not sure what lighting I'll settle on and depending on how things work out I may not need any walls, or different props.

Marc

Looking good. What did you do for the nest? Agrows with a single shader? Or multiple ones? Marc

Useful stuff! The main darkness difference is I forgot to render with a gamma correct of 1.3 as I had previously. Otherwise, there was no attempt to darken. (My previous machine died but fortunately I'd saved all but my last tweaks to the above; missed the gamma correct though).

I tried a Bryce cloudy night sky last night but had a problem with how it was sized in the backdrop (not sure what that was and didn't feel like spending much time on it.)

I agree the roof tiles are too big and the stars are still off. But... I'm itching to get on to my next project so I think I'll leave it as is for now. It was my first exercise focusing on lighting and composition and useful for me for that.

I received Amapi7 this week and am working on a chalice as a prop for another scene. Amapi 7.03 is a bit unstable but I'm finding it very easy to use; much better than my experience with Amapi 5. Once I have some Carrara renders I'll post a WIP of it for kicks. It will use Mark D's iridescence shader and hopefully show it off well. Still doing the modeling now...

Thanks again for the comments.

Marc

No problem... just trying to be helpful. To your original question about these WIP posts, as a WIP poster on this forum myself, I've been wondering if the better place for these WIPS is the yahoo carrara-pics group rather than this forum. I kind of like them in this forum because you can get some discussion on techniques and, frankly, this forum could use a little more traffic to keep it interesting. But I do wonder if others feel they aren't appropriate here... Marc