A question for you, Monsieur Poissant. Does glow work with radiosity? If so, why does it not render in my radiosity shots?

I was trying to do a radiosity render of a scene with a glow applied to the lantern models in my scene. When I do a standard render, the glow is present. When I render with radiosity the glow does not render, only the ambient surface of my lantern.

My current work around is to set the glow to 0% for radiosity shots and replace it with ambient intensity.

P.S. Awesome wood material tutorial, Yves! I'm using it in my current project Looks Great!

It would help if you posted a shot of what you are trying to achieve. Glow is supposed to work with radiosity but it is a post effect so there might be some differences.

Attachment 1 is a raytrace of what I am trying to achieve with the glowing.

The second pic is my radiosity render where I turned the glow off and used ambient intensity because the glow didn't render when I had it on during radiosity render. It just rendered the orb with no glow (ambient was not set on the orb when glow was on). I didn't save my attempt with glow on, sorry.

Because you did not include a radiosity render with Glow ON, I cannot comment on the affirmation that glow does not work with radiosity.

But one question though : Why do you want to use radiosity in this scene? I'm looking at the two scenes and frankly, I prefer the non-radiosity one. I can't see what you gain by using radiosity. You only get much higher render times without improving the result.

As for the radiosity one, it just does not look like a radiosity rendered scene. I think there are several texturing and surfacing as well as lighting issues in this scene that prevent the proper use of radiosity. Things to check first and foremost are the Ambiance Intensity settings on all your models, groups and material nodes. Then check your radiance setings too. Your scene is currently very far from being ready to use radiosity.

Maybe I've misunderstood some key point of radiosity. I've read through the sections several times, but I must not understand when to use and when not to. Personally, I trust your opinion about this scene and short render times would suit me just fine. Is there some material in the forums here or elsewhere that explains when radiosity should be used? I would like to explore this part of A:M, but I do not wish to abuse it, either. I guess I'm just a little confused.

I also noticed that it didn't have the look of radiosity about it. Your lights apear to have their darkness values set to the default value. Make sure that the shadow darkness is set to 100%, and set the ray casts to 2. Your radiosity also needs more final gathering sampling, or you need to increase your sampling area. Your light orbs should have some transparancy to them (50% should be enough), otherwise the photons will not pass through them. Here's a quick render of what you should be shooting for for the overall intensity if you were to use a white hallway.
[attachmentid=14946]
As far as my testing with it, glow does work with radiosity.
[attachmentid=14947]

I have the impression that you start by setting your scene with traditional lighting and texturing and when you are happy with the render, you turn ON radiosity. If you proceed that way, then that is definitively not the right approach.

When you start a scene that is destined to be radiosity rendered, you should start with that in mind from the begining. Start with the environment geometry then position the lights and start tweaking the light intensities with radiosity rendering. No textures, no colors at this point, you are just designing the light distribution in your scene. You must, at this point, fully understand how lights work and what their different properties mean as well as the result of their adjustment. Otherwise, you are just proceeding by trial and error and this is not a good way of working with radiosity. Radiosity must be approached in a more systematic way.


It's not just about my opinion. Look at the two renders. Is the difference that significative that it is worth the additional render time?


Blunt answer: If you don't know when you should use radiosity, then don't use it. That is probably because you don't yet have the required experience to use it properly.

There are no simple and sweet answers to that question. There are so many things to consider. Essentially, you are asking the wrong question. It is not "when" but "why". Radiosity is just one tiny part of the whole issue. You need to fully understand how light works, how materials and surface properties work and their interaction with light, etc. It basically would cover a full computer graphics course. As you gain experience and continue to read the tutorials and articles on radiosity and realistic rendering, you will be in a better position to understand the implication of what is being discussed. Eventually, you will know when is the time to use radiosity.

Let me re-ask you that question: Why do you want to use radiosity? You must be able to answer that question before you can decide when to use radiosity.


The correct way to handle those orbs is to set the light diameter just slightly larger than the orb diameter so the orb itself is inside the light. Then set the orb "radiance" setting to 0% to avoid bright white speckles in the scene.

Well, I really appreciate you taking some time with me on this Yves. You have given me a lot to think about. Until I am more practiced and learned, I think I should leave radiosity alone. I was under the impression that this feature would be easier to use and didn't realize the extent of the learning invovled. I think for now, I will spend a lot more time learning the basic properties of lights. Maybe a trip to the library is in store for me.

As for why do I want to use radiosity? I understood it to give the best quality rendering results with the most realistic lighting and shadowing of a cg scene, and that's what I ultimately strive for (even though I'm just learning and probably won't get those kind of results for a while).

I don't do this professionally like some of the artists using A:M, but I am interested in learning. Computer art and animation is fun...not easy, but fun. Who knows, maybe some day I'll be good enough to make some money with it too. Thanks to your help, tuts and general advise, I know a lot more about lighting and rendering than I did a week ago.

Well, thanks again for your help.

Arkaos, here's a popular tutorial on real-world lighting--what it looks like, and how to reproduce it:

http://www.itchy-animation.co.uk/light.htm

Why do you find the non-radiosity render not realistic?
Why would radiosity help making it more realistic?

I don't ask that you answer to those two questions. I just want to point out that those are the actual "why"s that need to be answered.

Radiosity by itself will not produce realistic lighting and shadowing. Radiosity do have the potential for producing the most realistic lighting and shading of a CG scene provided the scene itself is setup in the most realistic way.

The light tutorial pointed by luckbat is probably the best I've ever seen on the Internet. I highly recommend it. Start with that and integrate the concepts that are explained and demonstrated in it. You need to know what kind of results you are looking for. What sort of defects you are trying to correct in your render. This tutorial should help you develop an eye for that. When you will be able to point at specific spots in your render lighting and shadowing and name what is going on and know what is needed to correct it, then you will be ready to use radiosity.

Another good reference for lighting and texturing is Jeremy Birn book "Digital Lighting and Rendering". There is one aspect of lighting that I find is not very well covered by Birn, it is the effect of the environment on a rendered object. This is implied by all the material in the book but I think this is one aspect that would need to be elaborated separately and this is the basic principle driving the whole Image Based Lighting concept.

Thank you, again, Yves. I have been reading the info on the website luckbat posted. I also found that the local bookstores carry "Digital Lighting and Rendering". That means, this being a college town, the libraries should have it too. Now, I feel I am off in the right direction.

I got the Birn book for Christmas (found it on Amazon and had my wife click buy now). I found it very informative and mad eme more aware when I was watching animations of what lighting cues to look for. It's a good read that has enough technical information to make it useful, but not so much that you get blown away or bogged down in the details.

Now if we could just convert Yves into a book that we could keep next to the computer we'd be set!

Scott