I'm rendering scenes where I have glowing objects which I don't want to be used as light sources (the glow has been applied for the look and not for light). This hoses up renders if you're using indirect lighting. The difference between the results of GI .vs. raytracing are difficult to tell when you can't take advantage of the indirect lighting (in fact, GI appears worthless without indirect lighting). What kinds of experiences are others finding out there? The soft shadows in C are really starting to frustrate me big time!!!!! They just don't work worth a flying frog and they are so necessary when going for a more realistic look! If you can't use indirect lighting with GI, you sacrifice another avenue for a somewhat more realistic shadow (very limited though). Environmental lighting is still a good avenue but I'm having other problems with the shadows being too pixelated/striated. I'm SO HARD TO PLEASE on this shadow issue. RD had this problem figured out and could produce results. I really want to get my final images rendered lot better and stronger than my current results using GI. This is another example of how I think glow is not handled very well in C (my other complaint has always been how you couldn't selectively apply 3D aura for some glowing objects and not for others in the same scene.) So,,,,,, If you're up for it, comment on your experiences; 1.) Using GI without indirect lighting and 2.) Soft shadows Thanks, -Kix

Never tested the soft shadows successfully- I always tried to get them with GI/radiosity/whatever you care to call it, and it was a bit much for my machine. I remember the RDS ones being good but slow, I don't know if they changed it for Carrara or what... What would you use GI for if you're not using indirect lighting? That's what it IS. Do you mean having SOME glows light but others not? Then I'd recommend faking radiosity by sticking same-colored lights around the illuminators. And there's a function in "effects" to override the Aura setting for specific objects, last I checked.

I have very successfully faked radiosity in many situations but indirect lighting for the image above would really make it pop out. Glow is applied to bejuckets of objects in this scene! All the little white windws are glow white. They would totally screw this image up if I used indirect lighting. The same is true for the glowing red ball of which you can only see a crescent sliver of from this angle. There are way to many lights in this image and nooks and crannies to try to fake radiosity and GI/Indirect lighting seems to suffer in spaces which are enclosed of which this image is chock full! The image this size as posted wouldn't really show the shortfall of the soft shadow issue but when rendered full size with it applied, soft shadows generate ghosts and crappy artifacts ALL OVER THE PLACE! It's because the soft shadows appear to be more fixed in their fuzziness instead of really softened based on the distance of the object to the plane where the shadow is being cast and the location of the light. You can also get funky (very bad) results with soft shadows when applying them to spline objects which have cross sections in them with distinctly different shapes in the sections. RD had a different method of calculating soft shadows which had decent controls. It was changed in C. RD Soft Shadows were sharper closer to objects and became softer and softer the farther away you got. They were completely sharp right next to the object which removed the "hovering" problem C has. Environmental lighting can make shadows which do most of the things they should but I haven't figured a way to really get them to work to my total satsifaction. There are definite limits to EL. It changes from scene to scene a lot and takes quite a bit of work to get them right for each setup and it's very laborius for me. I have some setups where I could never really get it to work really well. -Kix

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Multi pass is probably the only solution that will work for this image if I truly want GI in it. I really had hoped there was something more to GI than just caustics or indirect lighting which would have been a significant improvement over raytracing. To finalize this image will take a lot of restructuring of textures to pull out all the glow for the GI render. I'll try to apply 3D aura to one of two objects glowing in a scene. I'd really like to be able to accomplish that! -Kix

Kix, Try playing with Glare, sometimes you can get the same or similiar result as the 3D aura and it can be applied on an individual object basis. Best regards, Eric Winemiller Digital Carvers Guild 3D extensions for Carrara http:digitalcarversguild.com

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I agree with you on the soft shadows. Quite disappointing. I'm building some product shots and the soft shadows cast from spline shapes are not very good. GI lighting takes too long to render. It would be very nice, though, to turn off glows on a part basis when in GI, I also have not found that yet. One thing I found about GI, If I have a background of a bright sunny day - the sky is blue. The blue sky dominates the colouring of the rendering, when really I want a bright white light for the sun and a blue colour to the shadows. I guess I could use lights and hybrid render instead of GI, but those soft shadows .... With regards to your ATAT, there is a page in the manual that talks about that problem (some where in the p500's towards the back of the manual) and is a common problem for all GI rendering software from what I have seen. Andrew

I should mention the previous image had two lights in it. One light is a sphere with the glow channel scaled to about 1300. This produced the excellent fill in areas of shadow but basically produced no shadows. The other light is a bulb with the soft shadows turned on. The lights are stacked on top of each other. -Kix

First off, Kix, REALLY NICE MODEL! I'm really impressed with your old Constitution Class ship, there. It's awesome! Is this something you're considering making available to those of us out here in 'rosity land? Second, I was going to suggest the multiple pass approach, myself. It seems like the answer. Yes, GI takes a long time to render, but it's worth it for the quality of the image. Doing a multi pass render will also take a long time, but it's probably your only approach. If you composite your multi passes in Photoshop, you'll be able to have a little more control over the "aura" effect on glowing areas, too. More control! More Control! - Dex

See I'm not sure whats the problem? You want the glowing white windows anyway, since they will in effect/reality be part of the lighting thats lighting up the scene. They would effect there surroundings. So I'm not sure.... Whats the additional lighting in that Starship/starbase scene. Ambient 0? Got a scene screen cap. The glowing panels, should help not hinder. Soft shadows have always worked fine for me. My image for example the soft shadows look beautiful. To me anyway:)! Brian

Here's what I'm going to do. SHADOWS Soft Shadows: I've decided to write up a technical study on shadows starting with Raydream (may the 3D gods smile upon me and help me to remember that code!). I'm going to do raytraced and soft shadows in Radream first. Then we're moving on to shadow possibilities in Carrara which would include regular soft shadows, shadows cast by environmental lighting, and shadows which are produced by GI. I will address pros and cons of all this stuff. CONSTITUTION CLASS STARSHIP MODEL Unfortunately I'm not ready to release this model to the public yet. There are several reasons for this. 1.) I built this model in RD and it has personal sentimental value. 2.) It is chockablock full of flaws and they really need to be fixed. 3.) It's clumsy and difficult to use for somebody who's unfamiliear with it. 4.) The more I work with it, the more RD shortcomings I have to redo all the time and the whole stinking thing needs a major overhaul. 5.) I have made a new years resolution to build a whole new model in Amapi this year to learn Amapi. I've done it twice now in C and the details are all in my head so a third time should be a whole lot better! 6.) You can go out on the net and find one that's just as good (better). This always depresses me and I have even more reluctance to release this model with such good competition out there. GI RENDERING The windows to contribute to the light in the scene but the interfere so dang much with the structure around them that it totally hoses up the starship model. I'm a Paint Shop Pro user and I'm sure I can do the compositing of the multipass rendering in that package but I don't know how. I'm going to have to research this some before I set up the passes for the render. There are eight lights inside the big construction hanger, two lights in the starship shuttle hanger, and one sunlight. The result of the render I've posted has been made by lots of tweaking of these lights and by turning down the shadow intensity for some of them. There is some ambient light in the image as well. -Kix

hmm. Then its a geometry problem, not a rendering problem?

The geometry is fine. The only thing that's wrong is the soft shadows calculation gets confused when analyzing the intersectin of the cross section shapes. The blade is one single spline model that changes shapes at that point. -Kix

Kind of like the wall problems that happen if the wall isn't pefectly fitted with the floor or if its not thick enough.

I know this doesn't have much to do with GI lighting, or the glow problems but while cruising I saw this page and thought of this discussion... http://www.menithings.com/How/Trek/Trek_Voyager_01.html

I'm having a lighting problem myself. Color mixing more then it should it seems. I'll post a screen shot laaate tonight. Brian

Hi,
regarding the sword scene, it is a geometry problem. Actually if you look at the sword you can see the error in the mesh...
In any case, a lot of people complain about softshadows, but no one takes the time to send us example files of those problems so that we can actually try to fix them or tell you how to do things.
I would like to remind you that you can always contact our technical support at : support@eovia.com and it is free ! (not like a lot of other companies). And we will look into the issues you are reporting and try to help you and try to make sure they do not occur in the next version of Carrara.
If you have problems with tech support, you can contact me directly at charles@eovia.com.
Regarding the GI, if you try to light a scene with hundreds of glowing objects, you are asking for trouble! I could probably get it to work but calculation time would be huge. Actually a radiosity algorithm would probably be better for that kind of scene.
If you want to use glowing objects, you need to make sure that there are not too many of them or it will not work. If they are really small it will cause problems too...
Increasing the number of photons will help detecting those small light sources...
In any case, we are working on those issues right now for carrara Studio 3 so now is the time to contact us and send us the files that are causing you problems ! I would really like to get the files you posted pictures for instance.
Thanks for your help
Charles

Thanks for the post! I'll be in touch. -Kix

Heck with indirect lighting. I'm trying to figure out good settings for caustics. My only problem with indirect lighting is the clash of spectrums I seem to experience. I know the whole over 100% thing is bad but I need to go over 100% to get the amplified light look I am going for. Although even if I have the lighting equaled out to 100% the colors mix and I get odd colors. I still need to post an example I'll try to do that later tonight to show you what I mean in a new thread, this one is getting to large:) Brian

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In the new book Digital Lighting and Rendering by Jeremy Birn, there is a lighting tutorial on faking soft shadows with multiple spotlights arranged in a row. He illustrates this by lighting a simple lamp on an end table with about 8 spotlights placed horizontally in a crescent arrangement. This wraps the light around the objects very convincingly and really looks like soft shadowed lighting. He provides lighting diagrams and everything. Pretty soon I'm going to break down and actually buy this book. ;-)

IIRC, he also explains how to cheat indirect lighting using a similar method with lights set to cast no shadows.

I'm sure there must be a way to cheat soft shadows and indirect lighting in Carrara's regular raytracer using an adaptation of this method. Sure, lots of lights increase your raytracer rendering time, but I bet it's faster and more reliable than using GI.

Also, Birn strongly advocates multiple-pass rendering on his website (and in his book no doubt) in part to cut rendering times.

Incidentally, I'm also in the process of redoing my 1701, originally made in RDD and rendered in I-D. I agree that Amapi is better suited to this, especially for the secondary hull. I won't post pictures because it's just not ready for prime time yet (and I'm a lawyer-hobbyist, not a full-time artist, so it's quite a while off yet). Helps to live in the DC area, though, where I can go look at the original for reference.

The link is to Birn's web site.

A.