How good works IBL at 3dsmax?

[Micha_cg]

Hi,

I ask me, how good works IBL at 3dsmax?
Can it be used together with PPT?
If yes, does it work like hypershot?
Is it right, if the sphere light would get a texture control, it would allow to use IBL?

[dalomar_cg]

Re: How good works IBL at 3dsmax?

I haven't really used it too much personally, but I'll try to answer your questions.

1. Not necessarily any better or worse than setting environment maps. If it was that much better I'm sure there would be more hoopla about it than there is.

2. Don't see why not

3. No...IBL isn't realtime. (hope I didn't misunderstand that one)

4. Sphere lights do not have any texture control in MAX, only Dome lights do.

[Micha_cg]

Re: How good works IBL at 3dsmax?

In my mind is, that Vlado wrote:

The V-Ray dome light has been extended to support arbitrary texture maps that determine the amount of light coming from each direction on the virtual dome hemisphere. V-Ray then uses importance sampling to trace more rays in the directions where most of the light is coming from. This ensures speed and quality that were never before possible with pure gathering GI methods.


* Easy setup for image-based lighting (IBL);
* Importance sampling of the dome texture for fast and clean results;
* Support for photon mapping for fast and accurate caustic effects.

So, it seems to be at IBL, Vray know, where it must sample bright parts of the HDRI, it speed up the calculation, shadows are more detailed. Also I remember me, that I read, that reflections are better sampled. My tests some weeks befor show me, that hypershot create very fast (after few seconds) and clean blury reflections of a High detailed, high conrast HDRI at a car paint.

The same car and HDRI rendered with Vray created slow calculated, extrem noisy reflections, so bad, that it was not useable. The random sampling of Vray lost in this comparsion. (This isn't advertisment for hypershot -> look at the car interior -> typical hypershot poor OpenGL look at interior parts with much indirect light)
So, I ask me, could the Vray IBL the best solution for high detailed, high contrast HDRI environments? In combination with PPT Vray could work like hypershot, fast and easy for object renderings.

[dalomar_cg]

Re: How good works IBL at 3dsmax?

As I said before, I haven't worked with it, and I'm not 100% sure what the real difference is. I'm not saying that there isn't one, I'm just saying that I don't think its a night and day kind of difference. V-Ray uses important sampling every where (bright values being sample more than dark values), so I'm not sure how that would actually change the dome light so that its better than just a GI environment.

IMHO (you can take it for what its worth) I think the real reason for the light dome is to have photon mapping support for a GI like light source. Since photon mapping requires having a physical source for shooting any photons standard GI won't do it, hence the dome implementation.

All this being said, we are looking to add support for light domes.

[Micha_cg]

Re: How good works IBL at 3dsmax?

... V-Ray uses important sampling every where (bright values being sample more than dark values), so I'm not sure how that would actually change the dome light so that its better than just a GI environment.

If I understand the infos about Vray right, "Importance sampling of the dome texture" means, that bright areas of the ENV MAP are more sampled than dark one. This should not be confused with the sampling of the output image, dark shadowed areas and bright areas of the SCENE OBJECTS. The current GI sampling used a random sampling of the env, that don't know, where are bright HDRI areas and where are dark one, that cause problems with HDRI with a bright small sun. IBL should allow to get sharp shadows from a HDRI sun. So, I expect a big advantage of IBL. And if it bring a huge benefit, than it could be a motivation to implement it. Do you have seen, hypershot got a Rhino exporter, the workflow is easy, HDRI env can be used without problems for object renderings. I think, Vray could support the same features - lighting from HDRI with sharp shadows, maybe progressiv and fast.

[Gijs]

Re: How good works IBL at 3dsmax?

I would very much appreciate implementation of the light dome (if it can be textured), because as Micha is expecting, this allows intelligent sampling of an HDRI and sharper shadows from a sunlight. Furthermore it allows to make renderings with HDRI, without having to use indirect illumination.

[Micha_cg]

Re: How good works IBL at 3dsmax?

Gijs, will it enhance the reflection sampling too?

[Gijs]

Re: How good works IBL at 3dsmax?

I don't think so, because it is only related to lighting. What I can imagine is that hypershot blurs the HDRI 'internally' per material. You can do this in Vray yourself by blurring the map and appling it on a material basis as you probably know.
I don't have hypershot, but maybe you can check this: Does hypershot make blurry reflections of objects just as fast? If it is not, then my assumption is probably right.

[dalomar_cg]

Re: How good works IBL at 3dsmax?

I believe you're right about blurries in hypershot, Gjis. Hypershot takes a lot of shortcuts to get things reasonable, so I would imagine that that would be a big one that they would take. The other big one that they take is only computing one GI bounce, which makes it okay for exterior/product scenes, but not nearly efficient enough for anything else.

[Micha_cg]

Re: How good works IBL at 3dsmax?

I don't know how hypershot do it and my demo is expired.

Generaly I wonder me, that blurry Vray reflections are quite slow and no big biased shortcut is available except the LC trick. Blury reflections show so less image informations, that it should possible to render it faster. If I remember me right, than mentalray support a feature, that blurry reflections can be rendered undersampled. Could be nice to see it a Vray too, but this is an other subject.

The material based blurry envrionment trick is quite limited, so it can't be used for a carpaint material with clear finish and blurry metal reflection.

About the interior limit: here an example of an semi-interior shot ... hypershot seems to use something like a OpenGL calculation at parts without any direct light. Also discrete shadows are created at the columns.

[Gijs]

Re: How good works IBL at 3dsmax?

Vray for 3dsmax has an interpolated blurry reflections option (per material) which is precalculated (similar to irradiance calculation) and has the same undersampling options.

[Micha_cg]

Re: How good works IBL at 3dsmax?

Sounds great.